drowning in blood and pain and madness. When he tried to

V. GALILEO AND THE NEW PHYSICS After Galileo had felt the strong hand of the Inquisition, in 1632, he was careful to confine his researches, or at least his publications, to topics that seemed free from theological implications. In doing so he reverted to the field of his earliest studies --namely, the field of mechanics; and the Dialoghi delle Nuove Scienze, which he finished in 1636, and which was printed two years later, attained a celebrity no less than that of the heretical dialogue that had preceded it. The later work was free from all apparent heresies, yet perhaps it did more towards the establishment of the Copernican doctrine, through the teaching of correct mechanical principles, than the other work had accomplished by a more direct method. Galileo's astronomical discoveries were, as we have seen, in a sense accidental; at least, they received their inception through the inventive genius of another. His mechanical discoveries, on the other hand, were the natural output of his own creative genius. At the very beginning of his career, while yet a very young man, though a professor of mathematics at Pisa, he had begun that onslaught upon the old Aristotelian ideas which he was to continue throughout his life. At the famous leaning tower in Pisa, the young iconoclast performed, in the year 1590, one of the most theatrical demonstrations in the history of science. Assembling a multitude of champions of the old ideas, he proposed to demonstrate the falsity of the Aristotelian doctrine that the velocity of falling bodies is proportionate to their weight. There is perhaps no fact more strongly illustrative of the temper of the Middle Ages than the fact that this doctrine, as taught by the Aristotelian philosopher, should so long have gone unchallenged. Now, however, it was put to the test; Galileo released a half-pound weight and a hundred-pound cannon-ball from near the top of the tower, and, needless to say, they reached the ground together. Of course, the spectators were but little pleased with what they saw. They could not doubt the evidence of their own senses as to the particular experiment in question; they could suggest, however, that the experiment involved a violation of the laws of nature through the practice of magic. To controvert so firmly established an idea savored of heresy. The young man guilty of such iconoclasm was naturally looked at askance by the scholarship of his time. Instead of being applauded, he was hissed, and he found it expedient presently to retire from Pisa. Fortunately, however, the new spirit of progress had made itself felt more effectively in some other portions of Italy, and so Galileo found a refuge and a following in Padua, and afterwards in Florence; and while, as we have seen, he was obliged to curb his enthusiasm regarding the subject that was perhaps nearest his heart--the promulgation of the Copernican theory--yet he was permitted in the main to carry on his experimental observations unrestrained. These experiments gave him a place of unquestioned authority among his contemporaries, and they have transmitted his name to posterity as that of one of the greatest of experimenters and the virtual founder of modern mechanical science. The experiments in question range over a wide field; but for the most part they have to do with moving bodies and with questions of force, or, as we should now say, of energy. The experiment at the leaning tower showed that the velocity of falling bodies is independent of the weight of the bodies, provided the weight is sufficient to overcome the resistance of the atmosphere. Later experiments with falling bodies led to the discovery of laws regarding the accelerated velocity of fall. Such velocities were found to bear a simple relation to the period of time from the beginning of the fall. Other experiments, in which balls were allowed to roll down inclined planes, corroborated the observation that the pull of gravitation gave a velocity proportionate to the length of fall, whether such fall were direct or in a slanting direction. These studies were associated with observations on projectiles, regarding which Galileo was the first to entertain correct notions. According to the current idea, a projectile fired, for example, from a cannon, moved in a straight horizontal line until the propulsive force was exhausted, and then fell to the ground in a perpendicular line. Galileo taught that the projectile begins to fall at once on leaving the mouth of the cannon and traverses a parabolic course. According to his idea, which is now familiar to every one, a cannon-ball dropped from the level of the cannon's muzzle will strike the ground simultaneously with a ball fired horizontally from the cannon. As to the paraboloid course pursued by the projectile, the resistance of the air is a factor which Galileo could not accurately compute, and which interferes with the practical realization of his theory. But this is a minor consideration. The great importance of his idea consists in the recognition that such a force as that of gravitation acts in precisely the same way upon all unsupported bodies, whether or not such bodies be at the same time acted upon by a force of translation. Out of these studies of moving bodies was gradually developed a correct notion of several important general laws of mechanics--laws a knowledge of which was absolutely essential to the progress of physical science. The belief in the rotation of the earth made necessary a clear conception that all bodies at the surface of the earth partake of that motion quite independently of their various observed motions in relation to one another. This idea was hard to grasp, as an oft-repeated argument shows. It was asserted again and again that, if the earth rotates, a stone dropped from the top of a tower could not fall at the foot of the tower, since the earth's motion would sweep the tower far away from its original position while the stone is in transit. This was one of the stock arguments against the earth's motion, yet it was one that could be refuted with the greatest ease by reasoning from strictly analogous experiments. It might readily be observed, for example, that a stone dropped from a moving cart does not strike the ground directly below the point from which it is dropped, but partakes of the forward motion of the cart. If any one doubt this he has but to jump from a moving cart to be given a practical demonstration of the fact that his entire body was in some way influenced by the motion of translation. Similarly, the simple experiment of tossing a ball from the deck of a moving ship will convince any one that the ball partakes of the motion of the ship, so that it can be manipulated precisely as if the manipulator were standing on the earth. In short, every-day experience gives us illustrations of what might be called compound motion, which makes it seem altogether plausible that, if the earth is in motion, objects at its surface will partake of that motion in a way that does not interfere with any other movements to which they may be subjected. As the Copernican doctrine made its way, this idea of compound motion naturally received more and more attention, and such experiments as those of Galileo prepared the way for a new interpretation of the mechanical principles involved. The great difficulty was that the subject of moving bodies had all along been contemplated from a wrong point of view. Since force must be applied to an object to put it in motion, it was perhaps not unnaturally assumed that similar force must continue to be applied to keep the object in motion. When, for example, a stone is thrown from the hand, the direct force applied necessarily ceases as soon as the projectile leaves the hand. The stone, nevertheless, flies on for a certain distance and then falls to the ground. How is this flight of the stone to be explained? The ancient philosophers puzzled more than a little over this problem, and the Aristotelians reached the conclusion that the motion of the hand had imparted a propulsive motion to the air, and that this propulsive motion was transmitted to the stone, pushing it on. Just how the air took on this propulsive property was not explained, and the vagueness of thought that characterized the time did not demand an explanation. Possibly the dying away of ripples in water may have furnished, by analogy, an explanation of the gradual dying out of the impulse which propels the stone. All of this was, of course, an unfortunate maladjustment of the point of view. As every one nowadays knows, the air retards the progress of the stone, enabling the pull of gravitation to drag it to the earth earlier than it otherwise could. Were the resistance of the air and the pull of gravitation removed, the stone as projected from the hand would fly on in a straight line, at an unchanged velocity, forever. But this fact, which is expressed in what we now term the first law of motion, was extremely difficult to grasp. The first important step towards it was perhaps implied in Galileo's study of falling bodies. These studies, as we have seen, demonstrated that a half-pound weight and a hundred-pound weight fall with the same velocity. It is, however, matter of common experience that certain bodies, as, for example, feathers, do not fall at the same rate of speed with these heavier bodies. This anomaly demands an explanation, and the explanation is found in the resistance offered the relatively light object by the air. Once the idea that the air may thus act as an impeding force was grasped, the investigator of mechanical principles had entered on a new and promising course. Galileo could not demonstrate the retarding influence of air in the way which became familiar a generation or two later; he could not put a feather and a coin in a vacuum tube and prove that the two would there fall with equal velocity, because, in his day, the air-pump had not yet been invented. The experiment was made only a generation after the time of Galileo, as we shall see; but, meantime, the great Italian had fully grasped the idea that atmospheric resistance plays a most important part in regard to the motion of falling and projected bodies. Thanks largely to his own experiments, but partly also to the efforts of others, he had come, before the end of his life, pretty definitely to realize that the motion of a projectile, for example, must be thought of as inherent in the projectile itself, and that the retardation or ultimate cessation of that motion is due to the action of antagonistic forces. In other words, he had come to grasp the meaning of the first law of motion. It remained, however, for the great Frenchman Descartes to give precise expression to this law two years after Galileo's death. As Descartes expressed it in his Principia Philosophiae, published in 1644, any body once in motion tends to go on in a straight line, at a uniform rate of speed, forever. Contrariwise, a stationary body will remain forever at rest unless acted on by some disturbing force. This all-important law, which lies at the very foundation of all true conceptions of mechanics, was thus worked out during the first half of the seventeenth century, as the outcome of numberless experiments for which Galileo's experiments with failing bodies furnished the foundation. So numerous and so gradual were the steps by which the reversal of view regarding moving bodies was effected that it is impossible to trace them in detail. We must be content to reflect that at the beginning of the Galilean epoch utterly false notions regarding the subject were entertained by the very greatest philosophers--by Galileo himself, for example, and by Kepler--whereas at the close of that epoch the correct and highly illuminative view had been attained. We must now consider some other experiments of Galileo which led to scarcely less-important results. The experiments in question had to do with the movements of bodies passing down an inclined plane, and with the allied subject of the motion of a pendulum. The elaborate experiments of Galileo regarding the former subject were made by measuring the velocity of a ball rolling down a plane inclined at various angles. He found that the velocity acquired by a ball was proportional to the height from which the ball descended regardless of the steepness of the incline. Experiments were made also with a ball rolling down a curved gutter, the curve representing the are of a circle. These experiments led to the study of the curvilinear motions of a weight suspended by a cord; in other words, of the pendulum. Regarding the motion of the pendulum, some very curious facts were soon ascertained. Galileo found, for example, that a pendulum of a given length performs its oscillations with the same frequency though the arc described by the pendulum be varied greatly.[1] He found, also, that the rate of oscillation for pendulums of different lengths varies according to a simple law. In order that one pendulum shall oscillate one-half as fast as another, the length of the pendulums must be as four to one. Similarly, by lengthening the pendulums nine times, the oscillation is reduced to one-third, In other words, the rate of oscillation of pendulums varies inversely as the square of their length. Here, then, is a simple relation between the motions of swinging bodies which suggests the relation which Kepler bad discovered between the relative motions of the planets. Every such discovery coming in this age of the rejuvenation of experimental science had a peculiar force in teaching men the all-important lesson that simple laws lie back of most of the diverse phenomena of nature, if only these laws can be discovered. Galileo further observed that his pendulum might be constructed of any weight sufficiently heavy readily to overcome the atmospheric resistance, and that, with this qualification, neither the weight nor the material had any influence upon the time of oscillation, this being solely determined by the length of the cord. Naturally, the practical utility of these discoveries was not overlooked by Galileo. Since a pendulum of a given length oscillates with unvarying rapidity, here is an obvious means of measuring time. Galileo, however, appears not to have met with any great measure of success in putting this idea into practice. It remained for the mechanical ingenuity of Huyghens to construct a satisfactory pendulum clock. As a theoretical result of the studies of rolling and oscillating bodies, there was developed what is usually spoken of as the third law of motion--namely, the law that a given force operates upon a moving body with an effect proportionate to its effect upon the same body when at rest. Or, as Whewell states the law: "The dynamical effect of force is as the statical effect; that is, the velocity which any force generates in a given time, when it puts the body in motion, is proportional to the pressure which this same force produces in a body at rest."[2] According to the second law of motion, each one of the different forces, operating at the same time upon a moving body, produces the same effect as if it operated upon the body while at rest.

STEVINUS AND THE LAW OF EQUILIBRIUM It appears, then, that the mechanical studies of Galileo, taken as a whole, were nothing less than revolutionary. They constituted the first great advance upon the dynamic studies of Archimedes, and then led to the secure foundation for one of the most important of modern sciences. We shall see that an important company of students entered the field immediately after the time of Galileo, and carried forward the work he had so well begun. But before passing on to the consideration of their labors, we must consider work in allied fields of two men who were contemporaries of Galileo and whose original labors were in some respects scarcely less important than his own. These men are the Dutchman Stevinus, who must always be remembered as a co-laborer with Galileo in the foundation of the science of dynamics, and the Englishman Gilbert, to whom is due the unqualified praise of first subjecting the phenomenon of magnetism to a strictly scientific investigation. Stevinus was born in the year 1548, and died in 1620. He was a man of a practical genius, and he attracted the attention of his non-scientific contemporaries, among other ways, by the construction of a curious land-craft, which, mounted on wheels, was to be propelled by sails like a boat. Not only did he write a book on this curious horseless carriage, but he put his idea into practical application, producing a vehicle which actually traversed the distance between Scheveningen and Petton, with no fewer than twenty-seven passengers, one of them being Prince Maurice of Orange. This demonstration was made about the year 1600. It does not appear, however, that any important use was made of the strange vehicle; but the man who invented it put his mechanical ingenuity to other use with better effect. It was he who solved the problem of oblique forces, and who discovered the important hydrostatic principle that the pressure of fluids is proportionate to their depth, without regard to the shape of the including vessel. The study of oblique forces was made by Stevinus with the aid of inclined planes. His most demonstrative experiment was a very simple one, in which a chain of balls of equal weight was hung from a triangle; the triangle being so constructed as to rest on a horizontal base, the oblique sides bearing the relation to each other of two to one. Stevinus found that his chain of balls just balanced when four balls were on the longer side and two on the shorter and steeper side. The balancing of force thus brought about constituted a stable equilibrium, Stevinus being the first to discriminate between such a condition and the unbalanced condition called unstable equilibrium. By this simple experiment was laid the foundation of the science of statics. Stevinus had a full grasp of the principle which his experiment involved, and he applied it to the solution of oblique forces in all directions. Earlier investigations of Stevinus were published in 1608. His collected works were published at Leyden in 1634. This study of the equilibrium of pressure of bodies at rest led Stevinus, not unnaturally, to consider the allied subject of the pressure of liquids. He is to be credited with the explanation of the so-called hydrostatic paradox. The familiar modern experiment which illustrates this paradox is made by inserting a long perpendicular tube of small caliber into the top of a tight barrel. On filling the barrel and tube with water, it is possible to produce a pressure which will burst the barrel, though it be a strong one, and though the actual weight of water in the tube is comparatively insignificant. This illustrates the fact that the pressure at the bottom of a column of liquid is proportionate to the height of the column, and not to its bulk, this being the hydrostatic paradox in question. The explanation is that an enclosed fluid under pressure exerts an equal force upon all parts of the circumscribing wall; the aggregate pressure may, therefore, be increased indefinitely by increasing the surface. It is this principle, of course, which is utilized in the familiar hydrostatic press. Theoretical explanations of the pressure of liquids were supplied a generation or two later by numerous investigators, including Newton, but the practical refoundation of the science of hydrostatics in modern times dates from the experiments of Stevinus.

GALILEO AND THE EQUILIBRIUM OF FLUIDS Experiments of an allied character, having to do with the equilibrium of fluids, exercised the ingenuity of Galileo. Some of his most interesting experiments have to do with the subject of floating bodies. It will be recalled that Archimedes, away back in the Alexandrian epoch, had solved the most important problems of hydrostatic equilibrium. Now, however, his experiments were overlooked or forgotten, and Galileo was obliged to make experiments anew, and to combat fallacious views that ought long since to have been abandoned. Perhaps the most illuminative view of the spirit of the times can be gained by quoting at length a paper of Galileo's, in which he details his own experiments with floating bodies and controverts the views of his opponents. The paper has further value as illustrating Galileo's methods both as experimenter and as speculative reasoner. The current view, which Galileo here undertakes to refute, asserts that water offers resistance to penetration, and that this resistance is instrumental in determining whether a body placed in water will float or sink. Galileo contends that water is non-resistant, and that bodies float or sink in virtue of their respective weights. This, of course, is merely a restatement of the law of Archimedes. But it remains to explain the fact that bodies of a certain shape will float, while bodies of the same material and weight, but of a different shape, will sink. We shall see what explanation Galileo finds of this anomaly as we proceed. In the first place, Galileo makes a cone of wood or of wax, and shows that when it floats with either its point or its base in the water, it displaces exactly the same amount of fluid, although the apex is by its shape better adapted to overcome the resistance of the water, if that were the cause of buoyancy. Again, the experiment may be varied by tempering the wax with filings of lead till it sinks in the water, when it will be found that in any figure the same quantity of cork must be added to it to raise the surface. "But," says Galileo, "this silences not my antagonists; they say that all the discourse hitherto made by me imports little to them, and that it serves their turn; that they have demonstrated in one instance, and in such manner and figure as pleases them best --namely, in a board and in a ball of ebony--that one when put into the water sinks to the bottom, and that the other stays to swim on the top; and the matter being the same, and the two bodies differing in nothing but in figure, they affirm that with all perspicuity they have demonstrated and sensibly manifested what they undertook. Nevertheless, I believe, and think I can prove, that this very experiment proves nothing against my theory. And first, it is false that the ball sinks and the board not; for the board will sink, too, if you do to both the figures as the words of our question require; that is, if you put them both in the water; for to be in the water implies to be placed in the water, and by Aristotle's own definition of place, to be placed imports to be environed by the surface of the ambient body; but when my antagonists show the floating board of ebony, they put it not into the water, but upon the water; where, being detained by a certain impediment (of which more anon), it is surrounded, partly with water, partly with air, which is contrary to our agreement, for that was that bodies should be in the water, and not part in the water, part in the air. "I will not omit another reason, founded also upon experience, and, if I deceive not myself, conclusive against the notion that figure, and the resistance of the water to penetration, have anything to do with the buoyancy of bodies. Choose a piece of wood or other matter, as, for instance, walnut-wood, of which a ball rises from the bottom of the water to the surface more slowly than a ball of ebony of the same size sinks, so that, clearly, the ball of ebony divides the water more readily in sinking than the ball of wood does in rising. Then take a board of walnut-tree equal to and like the floating one of my antagonists; and if it be true that this latter floats by reason of the figure being unable to penetrate the water, the other of walnut-tree, without a question, if thrust to the bottom, ought to stay there, as having the same impeding figure, and being less apt to overcome the said resistance of the water. But if we find by experience that not only the thin board, but every other figure of the same walnut-tree, will return to float, as unquestionably we shall, then I must desire my opponents to forbear to attribute the floating of the ebony to the figure of the board, since the resistance of the water is the same in rising as in sinking, and the force of ascension of the walnut-tree is less than the ebony's force for going to the bottom. "Now let us return to the thin plate of gold or silver, or the thin board of ebony, and let us lay it lightly upon the water, so that it may stay there without sinking, and carefully observe the effect. It will appear clearly that the plates are a considerable matter lower than the surface of the water, which rises up and makes a kind of rampart round them on every side. But if it has already penetrated and overcome the continuity of the water, and is of its own nature heavier than the water, why does it not continue to sink, but stop and suspend itself in that little dimple that its weight has made in the water? My answer is, because in sinking till its surface is below the water, which rises up in a bank round it, it draws after and carries along with it the air above it, so that that which, in this case, descends in the water is not only the board of ebony or the plate of iron, but a compound of ebony and air, from which composition results a solid no longer specifically heavier than the water, as was the ebony or gold alone. But, gentlemen, we want the same matter; you are to alter nothing but the shape, and, therefore, have the goodness to remove this air, which may be done simply by washing the surface of the board, for the water having once got between the board and the air will run together, and the ebony will go to the bottom; and if it does not, you have won the day. "But methinks I hear some of my antagonists cunningly opposing this, and telling me that they will not on any account allow their boards to be wetted, because the weight of the water so added, by making it heavier than it was before, draws it to the bottom, and that the addition of new weight is contrary to our agreement, which was that the matter should be the same. "To this I answer, first, that nobody can suppose bodies to be put into the water without their being wet, nor do I wish to do more to the board than you may do to the ball. Moreover, it is not true that the board sinks on account of the weight of the water added in the washing; for I will put ten or twenty drops on the floating board, and so long as they stand separate it shall not sink; but if the board be taken out and all that water wiped off, and the whole surface bathed with one single drop, and put it again upon the water, there is no question but it will sink, the other water running to cover it, being no longer hindered by the air. In the next place, it is altogether false that water can in any way increase the weight of bodies immersed in it, for water has no weight in water, since it does not sink. Now just as he who should say that brass by its own nature sinks, but that when formed into the shape of a kettle it acquires from that figure the virtue of lying in water without sinking, would say what is false, because that is not purely brass which then is put into the water, but a compound of brass and air; so is it neither more nor less false that a thin plate of brass or ebony swims by virtue of its dilated and broad figure. Also, I cannot omit to tell my opponents that this conceit of refusing to bathe the surface of the board might beget an opinion in a third person of a poverty of argument on their side, especially as the conversation began about flakes of ice, in which it would be simple to require that the surfaces should be kept dry; not to mention that such pieces of ice, whether wet or dry, always float, and so my antagonists say, because of their shape. "Some may wonder that I affirm this power to be in the air of keeping plate of brass or silver above water, as if in a certain sense I would attribute to the air a kind of magnetic virtue for sustaining heavy bodies with which it is in contact. To satisfy all these doubts I have contrived the following experiment to demonstrate how truly the air does support these bodies; for I have found, when one of these bodies which floats when placed lightly on the water is thoroughly bathed and sunk to the bottom, that by carrying down to it a little air without otherwise touching it in the least, I am able to raise and carry it back to the top, where it floats as before. To this effect, I take a ball of wax, and with a little lead make it just heavy enough to sink very slowly to the bottom, taking care that its surface be quite smooth and even. This, if put gently into the water, submerges almost entirely, there remaining visible only a little of the very top, which, so long as it is joined to the air, keeps the ball afloat; but if we take away the contact of the air by wetting this top, the ball sinks to the bottom and remains there. Now to make it return to the surface by virtue of the air which before sustained it, thrust into the water a glass with the mouth downward, which will carry with it the air it contains, and move this down towards the ball until you see, by the transparency of the glass, that the air has reached the top of it; then gently draw the glass upward, and you will see the ball rise, and afterwards stay on the top of the water, if you carefully part the glass and water without too much disturbing it."[3] It will be seen that Galileo, while holding in the main to a correct thesis, yet mingles with it some false ideas. At the very outset, of course, it is not true that water has no resistance to penetration; it is true, however, in the sense in which Galileo uses the term--that is to say, the resistance of the water to penetration is not the determining factor ordinarily in deciding whether a body sinks or floats. Yet in the case of the flat body it is not altogether inappropriate to say that the water resists penetration and thus supports the body. The modern physicist explains the phenomenon as due to surface-tension of the fluid. Of course, Galileo's disquisition on the mixing of air with the floating body is utterly fanciful. His experiments were beautifully exact; his theorizing from them was, in this instance, altogether fallacious. Thus, as already intimated, his paper is admirably adapted to convey a double lesson to the student of science.

WILLIAM GILBERT AND THE STUDY OF MAGNETISM It will be observed that the studies of Galileo and Stevinus were chiefly concerned with the force of gravitation. Meanwhile, there was an English philosopher of corresponding genius, whose attention was directed towards investigation of the equally mysterious force of terrestrial magnetism. With the doubtful exception of Bacon, Gilbert was the most distinguished man of science in England during the reign of Queen Elizabeth. He was for many years court physician, and Queen Elizabeth ultimately settled upon him a pension that enabled him to continue his researches in pure science. His investigations in chemistry, although supposed to be of great importance, are mostly lost; but his great work, De Magnete, on which he labored for upwards of eighteen years, is a work of sufficient importance, as Hallam says, "to raise a lasting reputation for its author." From its first appearance it created a profound impression upon the learned men of the continent, although in England Gilbert's theories seem to have been somewhat less favorably received. Galileo freely expressed his admiration for the work and its author; Bacon, who admired the author, did not express the same admiration for his theories; but Dr. Priestley, later, declared him to be "the father of modern electricity." Strangely enough, Gilbert's book had never been translated into English, or apparently into any other language, until recent years, although at the time of its publication certain learned men, unable to read the book in the original, had asked that it should be. By this neglect, or oversight, a great number of general readers as well as many scientists, through succeeding centuries, have been deprived of the benefit of writings that contained a good share of the fundamental facts about magnetism as known to-day. Gilbert was the first to discover that the earth is a great magnet, and he not only gave the name of "pole" to the extremities of the magnetic needle, but also spoke of these "poles" as north and south pole, although he used these names in the opposite sense from that in which we now use them, his south pole being the extremity which pointed towards the north, and vice versa. He was also first to make use of the terms "electric force," "electric emanations," and "electric attractions." It is hardly necessary to say that some of the views taken by Gilbert, many of his theories, and the accuracy of some of his experiments have in recent times been found to be erroneous. As a pioneer in an unexplored field of science, however, his work is remarkably accurate. "On the whole," says Dr. John Robinson, "this performance contains more real information than any writing of the age in which he lived, and is scarcely exceeded by any that has appeared since."[4] In the preface to his work Gilbert says: "Since in the discovery of secret things, and in the investigation of hidden causes, stronger reasons are obtained from sure experiments and demonstrated arguments than from probable conjectures and the opinions of philosophical speculators of the common sort, therefore, to the end of that noble substance of that great loadstone, our common mother (the earth), still quite unknown, and also that the forces extraordinary and exalted of this globe may the better be understood, we have decided, first, to begin with the common stony and ferruginous matter, and magnetic bodies, and the part of the earth that we may handle and may perceive with senses, and then to proceed with plain magnetic experiments, and to penetrate to the inner parts of the earth."[5] Before taking up the demonstration that the earth is simply a giant loadstone, Gilbert demonstrated in an ingenious way that every loadstone, of whatever size, has definite and fixed poles. He did this by placing the stone in a metal lathe and converting it into a sphere, and upon this sphere demonstrated how the poles can be found. To this round loadstone he gave the name of terrella--that is, little earth. "To find, then, poles answering to the earth," he says, "take in your hand the round stone, and lay on it a needle or a piece of iron wire: the ends of the wire move round their middle point, and suddenly come to a standstill. Now, with ochre or with chalk, mark where the wire lies still and sticks. Then move the middle or centre of the wire to another spot, and so to a third and fourth, always marking the stone along the length of the wire where it stands still; the lines so marked will exhibit meridian circles, or circles like meridians, on the stone or terrella; and manifestly they will all come together at the poles of the stone. The circle being continued in this way, the poles appear, both the north and the south, and betwixt these, midway, we may draw a large circle for an equator, as is done by the astronomer in the heavens and on his spheres, and by the geographer on the terrestrial globe."[6] Gilbert had tried the familiar experiment of placing the loadstone on a float in water, and observed that the poles always revolved until they pointed north and south, which he explained as due to the earth's magnetic attraction. In this same connection he noticed that a piece of wrought iron mounted on a cork float was attracted by other metals to a slight degree, and he observed also that an ordinary iron bar, if suspended horizontally by a thread, assumes invariably a north and south direction. These, with many other experiments of a similar nature, convinced him that the earth "is a magnet and a loadstone," which he says is a "new and till now unheard-of view of the earth." Fully to appreciate Gilbert's revolutionary views concerning the earth as a magnet, it should be remembered that numberless theories to explain the action of the electric needle had been advanced. Columbus and Paracelsus, for example, believed that the magnet was attracted by some point in the heavens, such as a magnetic star. Gilbert himself tells of some of the beliefs that had been held by his predecessors, many of whom he declares "wilfully falsify." One of his first steps was to refute by experiment such assertions as that of Cardan, that "a wound by a magnetized needle was painless"; and also the assertion of Fracastoni that loadstone attracts silver; or that of Scalinger, that the diamond will attract iron; and the statement of Matthiolus that "iron rubbed with garlic is no longer attracted to the loadstone." Gilbert made extensive experiments to explain the dipping of the needle, which had been first noticed by William Norman. His deduction as to this phenomenon led him to believe that this was also explained by the magnetic attraction of the earth, and to predict where the vertical dip would be found. These deductions seem the more wonderful because at the time he made them the dip had just been discovered, and had not been studied except at London. His theory of the dip was, therefore, a scientific prediction, based on a preconceived hypothesis. Gilbert found the dip to be 72 degrees at London; eight years later Hudson found the dip at 75 degrees 22' north latitude to be 89 degrees 30'; but it was not until over two hundred years later, in 1831, that the vertical dip was first observed by Sir James Ross at about 70 degrees 5' north latitude, and 96 degrees 43' west longitude. This was not the exact point assumed by Gilbert, and his scientific predictions, therefore, were not quite correct; but such comparatively slight and excusable errors mar but little the excellence of his work as a whole. A brief epitome of some of his other important discoveries suffices to show that the exalted position in science accorded him by contemporaries, as well as succeeding generations of scientists, was well merited. He was first to distinguish between magnetism and electricity, giving the latter its name. He discovered also the "electrical charge," and pointed the way to the discovery of insulation by showing that the charge could be retained some time in the excited body by covering it with some non-conducting substance, such as silk; although, of course, electrical conduction can hardly be said to have been more than vaguely surmised, if understood at all by him. The first electrical instrument ever made, and known as such, was invented by him, as was also the first magnetometer, and the first electrical indicating device. Although three centuries have elapsed since his death, the method of magnetizing iron first introduced by him is in common use to-day. He made exhaustive experiments with a needle balanced on a pivot to see how many substances he could find which, like amber, on being rubbed affected the needle. In this way he discovered that light substances were attracted by alum, mica, arsenic, sealing-wax, lac sulphur, slags, beryl, amethyst, rock-crystal, sapphire, jet, carbuncle, diamond, opal, Bristol stone, glass, glass of antimony, gum-mastic, hard resin, rock-salt, and, of course, amber. He discovered also that atmospheric conditions affected the production of electricity, dryness being unfavorable and moisture favorable. Galileo's estimate of this first electrician is the verdict of succeeding generations. "I extremely admire and envy this author," he said. "I think him worthy of the greatest praise for the many new and true observations which he has made, to the disgrace of so many vain and fabling authors."

STUDIES OF LIGHT, HEAT, AND ATMOSPHERIC PRESSURE We have seen that Gilbert was by no means lacking in versatility, yet the investigations upon which his fame is founded were all pursued along one line, so that the father of magnetism may be considered one of the earliest of specialists in physical science. Most workers of the time, on the other band, extended their investigations in many directions. The sum total of scientific knowledge of that day had not bulked so large as to exclude the possibility that one man might master it all. So we find a Galileo, for example, making revolutionary discoveries in astronomy, and performing fundamental experiments in various fields of physics. Galileo's great contemporary, Kepler, was almost equally versatile, though his astronomical studies were of such pre-eminent importance that his other investigations sink into relative insignificance. Yet he performed some notable experiments in at least one department of physics. These experiments had to do with the refraction of light, a subject which Kepler was led to investigate, in part at least, through his interest in the telescope. We have seen that Ptolemy in the Alexandrian time, and Alhazen, the Arab, made studies of refraction. Kepler repeated their experiments, and, striving as always to generalize his observations, he attempted to find the law that governed the observed change of direction which a ray of light assumes in passing from one medium to another. Kepler measured the angle of refraction by means of a simple yet ingenious trough-like apparatus which enabled him to compare readily the direct and refracted rays. He discovered that when a ray of light passes through a glass plate, if it strikes the farther surface of the glass at an angle greater than 45 degrees it will be totally refracted instead of passing through into the air. He could not well fail to know that different mediums refract light differently, and that for the same medium the amount of light valies with the change in the angle of incidence. He was not able, however, to generalize his observations as he desired, and to the last the law that governs refraction escaped him. It remained for Willebrord Snell, a Dutchman, about the year 1621, to discover the law in question, and for Descartes, a little later, to formulate it. Descartes, indeed, has sometimes been supposed to be the discoverer of the law. There is reason to believe that he based his generalizations on the experiment of Snell, though he did not openly acknowledge his indebtedness. The law, as Descartes expressed it, states that the sine of the angle of incidence bears a fixed ratio to the sine of the angle of refraction for any given medium. Here, then, was another illustration of the fact that almost infinitely varied phenomena may be brought within the scope of a simple law. Once the law had been expressed, it could be tested and verified with the greatest ease; and, as usual, the discovery being made, it seems surprising that earlier investigators--in particular so sagacious a guesser as Kepler--should have missed it. Galileo himself must have been to some extent a student of light, since, as we have seen, he made such notable contributions to practical optics through perfecting the telescope; but he seems not to have added anything to the theory of light. The subject of heat, however, attracted his attention in a somewhat different way, and he was led to the invention of the first contrivance for measuring temperatures. His thermometer was based on the afterwards familiar principle of the expansion of a liquid under the influence of heat; but as a practical means of measuring temperature it was a very crude affair, because the tube that contained the measuring liquid was exposed to the air, hence barometric changes of pressure vitiated the experiment. It remained for Galileo's Italian successors of the Accademia del Cimento of Florence to improve upon the apparatus, after the experiments of Torricelli--to which we shall refer in a moment--had thrown new light on the question of atmospheric pressure. Still later the celebrated Huygens hit upon the idea of using the melting and the boiling point of water as fixed points in a scale of measurements, which first gave definiteness to thermometric tests.

TORRICELLI In the closing years of his life Galileo took into his family, as his adopted disciple in science, a young man, Evangelista Torricelli (1608-1647), who proved himself, during his short lifetime, to be a worthy follower of his great master. Not only worthy on account of his great scientific discoveries, but grateful as well, for when he had made the great discovery that the "suction" made by a vacuum was really nothing but air pressure, and not suction at all, he regretted that so important a step in science might not have been made by his great teacher, Galileo, instead of by himself. "This generosity of Torricelli," says Playfair, "was, perhaps, rarer than his genius: there are more who might have discovered the suspension of mercury in the barometer than who would have been willing to part with the honor of the discovery to a master or a friend." Torricelli's discovery was made in 1643, less than two years after the death of his master. Galileo had observed that water will not rise in an exhausted tube, such as a pump, to a height greater than thirty-three feet, but he was never able to offer a satisfactory explanation of the principle. Torricelli was able to demonstrate that the height at which the water stood depended upon nothing but its weight as compared with the weight of air. If this be true, it is evident that any fluid will be supported at a definite height, according to its relative weight as compared with air. Thus mercury, which is about thirteen times more dense than water, should only rise to one-thirteenth the height of a column of water--that is, about thirty inches. Reasoning in this way, Torricelli proceeded to prove that his theory was correct. Filling a long tube, closed at one end, with mercury, he inverted the tube with its open orifice in a vessel of mercury. The column of mercury fell at once, but at a height of about thirty inches it stopped and remained stationary, the pressure of the air on the mercury in the vessel maintaining it at that height. This discovery was a shattering blow to the old theory that had dominated that field of physics for so many centuries. It was completely revolutionary to prove that, instead of a mysterious something within the tube being responsible for the suspension of liquids at certain heights, it was simply the ordinary atmospheric pressure mysterious enough, it is true--pushing upon them from without. The pressure exerted by the atmosphere was but little understood at that time, but Torricelli's discovery aided materially in solving the mystery. The whole class of similar phenomena of air pressure, which had been held in the trammel of long-established but false doctrines, was now reduced to one simple law, and the door to a solution of a host of unsolved problems thrown open. It had long been suspected and believed that the density of the atmosphere varies at certain times. That the air is sometimes "heavy" and at other times "light" is apparent to the senses without scientific apparatus for demonstration. It is evident, then, that Torricelli's column of mercury should rise and fall just in proportion to the lightness or heaviness of the air. A short series of observations proved that it did so, and with those observations went naturally the observations as to changes in the weather. It was only necessary, therefore, to scratch a scale on the glass tube, indicating relative atmospheric pressures, and the Torricellian barometer was complete. Such a revolutionary theory and such an important discovery were, of course, not to be accepted without controversy, but the feeble arguments of the opponents showed how untenable the old theory had become. In 1648 Pascal suggested that if the theory of the pressure of air upon the mercury was correct, it could be demonstrated by ascending a mountain with the mercury tube. As the air was known to get progressively lighter from base to summit, the height of the column should be progressively lessened as the ascent was made, and increase again on the descent into the denser air. The experiment was made on the mountain called the Puy-de-Dome, in Auvergne, and the column of mercury fell and rose progressively through a space of about three inches as the ascent and descent were made. This experiment practically sealed the verdict on the new theory, but it also suggested something more. If the mercury descended to a certain mark on the scale on a mountain-top whose height was known, why was not this a means of measuring the heights of all other elevations? And so the beginning was made which, with certain modifications and corrections in details, is now the basis of barometrical measurements of heights. In hydraulics, also, Torricelli seems to have taken one of the first steps. He did this by showing that the water which issues from a hole in the side or bottom of a vessel does so at the same velocity as that which a body would acquire by falling from the level of the surface of the water to that of the orifice. This discovery was of the greatest importance to a correct understanding of the science of the motions of fluids. He also discovered the valuable mechanical principle that if any number of bodies be connected so that by their motion there is neither ascent nor descent of their centre of gravity, these bodies are in equilibrium. Besides making these discoveries, he greatly improved the microscope and the telescope, and invented a simple microscope made of a globule of glass. In 1644 he published a tract on the properties of the cycloid in which he suggested a solution of the problem of its quadrature. As soon as this pamphlet appeared its author was accused by Gilles Roberval (1602-1675) of having appropriated a solution already offered by him. This led to a long debate, during which Torricelli was seized with a fever, from the effects of which he died, in Florence, October 25, 1647. There is reason to believe, however, that while Roberval's discovery was made before Torricelli's, the latter reached his conclusions independently.

VI. TWO PSEUDO-SCIENCES--ALCHEMY AND ASTROLOGY In recent chapters we have seen science come forward with tremendous strides. A new era is obviously at hand. But we shall misconceive the spirit of the times if we fail to understand that in the midst of all this progress there was still room for mediaeval superstition and for the pursuit of fallacious ideals. Two forms of pseudo-science were peculiarly prevalent --alchemy and astrology. Neither of these can with full propriety be called a science, yet both were pursued by many of the greatest scientific workers of the period. Moreover, the studies of the alchemist may with some propriety be said to have laid the foundation for the latter-day science of chemistry; while astrology was closely allied to astronomy, though its relations to that science are not as intimate as has sometimes been supposed. Just when the study of alchemy began is undetermined. It was certainly of very ancient origin, perhaps Egyptian, but its most flourishing time was from about the eighth century A.D. to the eighteenth century. The stories of the Old Testament formed a basis for some of the strange beliefs regarding the properties of the magic "elixir," or "philosopher's stone." Alchemists believed that most of the antediluvians, perhaps all of them, possessed a knowledge of this stone. How, otherwise, could they have prolonged their lives to nine and a half centuries? And Moses was surely a first-rate alchemist, as is proved by the story of the Golden Calf.[1] After Aaron had made the calf of gold, Moses performed the much more difficult task of grinding it to powder and "strewing it upon the waters," thus showing that he had transmuted it into some lighter substance. But antediluvians and Biblical characters were not the only persons who were thought to have discovered the coveted. "elixir." Hundreds of aged mediaeval chemists were credited with having made the discovery, and were thought to be living on through the centuries by its means. Alaies de Lisle, for example, who died in 1298, at the age of 110, was alleged to have been at the point of death at the age of fifty, but just at this time he made the fortunate discovery of the magic stone, and so continued to live in health and affluence for sixty years more. And De Lisle was but one case among hundreds. An aged and wealthy alchemist could claim with seeming plausibility that he was prolonging his life by his magic; whereas a younger man might assert that, knowing the great secret, he was keeping himself young through the centuries. In either case such a statement, or rumor, about a learned and wealthy alchemist was likely to be believed, particularly among strangers; and as such a man would, of course, be the object of much attention, the claim was frequently made by persons seeking notoriety. One of the most celebrated of these impostors was a certain Count de Saint-Germain, who was connected with the court of Louis XV. His statements carried the more weight because, having apparently no means of maintenance, he continued to live in affluence year after year--for two thousand years, as he himself admitted--by means of the magic stone. If at any time his statements were doubted, he was in the habit of referring to his valet for confirmation, this valet being also under the influence of the elixir of life. "Upon one occasion his master was telling a party of ladies and gentlemen, at dinner, some conversation he had had in Palestine, with King Richard I., of England, whom he described as a very particular friend of his. Signs of astonishment and incredulity were visible on the faces of the company, upon which Saint-Germain very coolly turned to his servant, who stood behind his chair, and asked him if he had not spoken the truth. 'I really cannot say,' replied the man, without moving a muscle; 'you forget, sir, I have been only five hundred years in your service.' 'Ah, true,' said his master, 'I remember now; it was a little before your time!' "[2] In the time of Saint-Germain, only a little over a century ago, belief in alchemy had almost disappeared, and his extraordinary tales were probably regarded in the light of amusing stories. Still there was undoubtedly a lingering suspicion in the minds of many that this man possessed some peculiar secret. A few centuries earlier his tales would hardly have been questioned, for at that time the belief in the existence of this magic something was so strong that the search for it became almost a form of mania; and once a man was seized with it, lie gambled away health, position, and life itself in pursuing the coveted stake. An example of this is seen in Albertus Magnus, one of the most learned men of his time, who it is said resigned his position as bishop of Ratisbon in order that he might pursue his researches in alchemy. If self-sacrifice was not sufficient to secure the prize, crime would naturally follow, for there could be no limit to the price of the stakes in this game. The notorious Marechal de Reys, failing to find the coveted stone by ordinary methods of laboratory research, was persuaded by an impostor that if he would propitiate the friendship of the devil the secret would be revealed. To this end De Reys began secretly capturing young children as they passed his castle and murdering them. When he was at last brought to justice it was proved that he had murdered something like a hundred children within a period of three years. So, at least, runs one version of the story of this perverted being. Naturally monarchs, constantly in need of funds, were interested in these alchemists. Even sober England did not escape, and Raymond Lully, one of the most famous of the thirteenth and fourteenth century alchemists, is said to have been secretly invited by King Edward I. (or II.) to leave Milan and settle in England. According to some accounts, apartments were assigned to his use in the Tower of London, where he is alleged to have made some six million pounds sterling for the monarch, out of iron, mercury, lead, and pewter. Pope John XXII., a friend and pupil of the alchemist Arnold de Villeneuve, is reported to have learned the secrets of alchemy from his master. Later he issued two bulls against "pretenders" in the art, which, far from showing his disbelief, were cited by alchemists as proving that he recognized pretenders as distinct from true masters of magic. To moderns the attitude of mind of the alchemist is difficult to comprehend. It is, perhaps, possible to conceive of animals or plants possessing souls, but the early alchemist attributed the same thing--or something kin to it--to metals also. Furthermore, just as plants germinated from seeds, so metals were supposed to germinate also, and hence a constant growth of metals in the ground. To prove this the alchemist cited cases where previously exhausted gold-mines were found, after a lapse of time, to contain fresh quantities of gold. The "seed" of the remaining particles of gold had multiplied and increased. But this germinating process could only take place under favorable conditions, just as the seed of a plant must have its proper surroundings before germinating; and it was believed that the action of the philosopher's stone was to hasten this process, as man may hasten the growth of plants by artificial means. Gold was looked upon as the most perfect metal, and all other metals imperfect, because not yet "purified." By some alchemists they were regarded as lepers, who, when cured of their leprosy, would become gold. And since nature intended that all things should be perfect, it was the aim of the alchemist to assist her in this purifying process, and incidentally to gain wealth and prolong his life. By other alchemists the process of transition from baser metals into gold was conceived to be like a process of ripening fruit. The ripened product was gold, while the green fruit, in various stages of maturity, was represented by the base metals. Silver, for example, was more nearly ripe than lead; but the difference was only one of "digestion," and it was thought that by further "digestion" lead might first become silver and eventually gold. In other words, Nature had not completed her work, and was wofully slow at it at best; but man, with his superior faculties, was to hasten the process in his laboratories--if he could but hit upon the right method of doing so. It should not be inferred that the alchemist set about his task of assisting nature in a haphazard way, and without training in the various alchemic laboratory methods. On the contrary, he usually served a long apprenticeship in the rudiments of his calling. He was obliged to learn, in a general way, many of the same things that must be understood in either chemical or alchemical laboratories. The general knowledge that certain liquids vaporize at lower temperatures than others, and that the melting-points of metals differ greatly, for example, was just as necessary to alchemy as to chemistry. The knowledge of the gross structure, or nature, of materials was much the same to the alchemist as to the chemist, and, for that matter, many of the experiments in calcining, distilling, etc., were practically identical. To the alchemist there were three principles--salt, sulphur, and mercury--and the sources of these principles were the four elements--earth, water, fire, and air. These four elements were accountable for every substance in nature. Some of the experiments to prove this were so illusive, and yet apparently so simple, that one is not surprised that it took centuries to disprove them. That water was composed of earth and air seemed easily proven by the simple process of boiling it in a tea-kettle, for the residue left was obviously an earthy substance, whereas the steam driven off was supposed to be air. The fact that pure water leaves no residue was not demonstrated until after alchemy had practically ceased to exist. It was possible also to demonstrate that water could be turned into fire by thrusting a red-hot poker under a bellglass containing a dish of water. Not only did the quantity of water diminish, but, if a lighted candle was thrust under the glass, the contents ignited and burned, proving, apparently, that water had been converted into fire. These, and scores of other similar experiments, seemed so easily explained, and to accord so well with the "four elements" theory, that they were seldom questioned until a later age of inductive science. But there was one experiment to which the alchemist pinned his faith in showing that metals could be "killed" and "revived," when proper means were employed. It had been known for many centuries that if any metal, other than gold or silver, were calcined in an open crucible, it turned, after a time, into a peculiar kind of ash. This ash was thought by the alchemist to represent the death of the metal. But if to this same ash a few grains of wheat were added and heat again applied to the crucible, the metal was seen to "rise from its ashes" and resume its original form--a well-known phenomenon of reducing metals from oxides by the use of carbon, in the form of wheat, or, for that matter, any other carbonaceous substance. Wheat was, therefore, made the symbol of the resurrection of the life eternal. Oats, corn, or a piece of charcoal would have "revived" the metals from the ashes equally well, but the mediaeval alchemist seems not to have known this. However, in this experiment the metal seemed actually to be destroyed and revivified, and, as science had not as yet explained this striking phenomenon, it is little wonder that it deceived the alchemist. Since the alchemists pursued their search of the magic stone in such a methodical way, it would seem that they must have some idea of the appearance of the substance they sought. Probably they did, each according to his own mental bias; but, if so, they seldom committed themselves to writing, confining their discourses largely to speculations as to the properties of this illusive substance. Furthermore, the desire for secrecy would prevent them from expressing so important a piece of information. But on the subject of the properties, if not on the appearance of the "essence," they were voluminous writers. It was supposed to be the only perfect substance in existence, and to be confined in various substances, in quantities proportionate to the state of perfection of the substance. Thus, gold being most nearly perfect would contain more, silver less, lead still less, and so on. The "essence" contained in the more nearly perfect metals was thought to be more potent, a very small quantity of it being capable of creating large quantities of gold and of prolonging life indefinitely. It would appear from many of the writings of the alchemists that their conception of nature and the supernatural was so confused and entangled in an inexplicable philosophy that they themselves did not really understand the meaning of what they were attempting to convey. But it should not be forgotten that alchemy was kept as much as possible from the ignorant general public, and the alchemists themselves had knowledge of secret words and expressions which conveyed a definite meaning to one of their number, but which would appear a meaningless jumble to an outsider. Some of these writers declared openly that their writings were intended to convey an entirely erroneous impression, and were sent out only for that purpose. However, while it may have been true that the vagaries of their writings were made purposely, the case is probably more correctly explained by saying that the very nature of the art made definite statements impossible. They were dealing with something that did not exist--could not exist. Their attempted descriptions became, therefore, the language of romance rather than the language of science. But if the alchemists themselves were usually silent as to the appearance of the actual substance of the philosopher's stone, there were numberless other writers who were less reticent. By some it was supposed to be a stone, by others a liquid or elixir, but more commonly it was described as a black powder. It also possessed different degrees of efficiency according to its degrees of purity, certain forms only possessing the power of turning base metals into gold, while others gave eternal youth and life or different degrees of health. Thus an alchemist, who had made a partial discovery of this substance, could prolong life a certain number of years only, or, possessing only a small and inadequate amount of the magic powder, he was obliged to give up the ghost when the effect of this small quantity had passed away. This belief in the supernatural power of the philosopher's stone to prolong life and heal diseases was probably a later phase of alchemy, possibly developed by attempts to connect the power of the mysterious essence with Biblical teachings. The early Roman alchemists, who claimed to be able to transmute metals, seem not to have made other claims for their magic stone. By the fifteenth century the belief in the philosopher's stone had become so fixed that governments began to be alarmed lest some lucky possessor of the secret should flood the country with gold, thus rendering the existing coin of little value. Some little consolation was found in the thought that in case all the baser metals were converted into gold iron would then become the "precious metal," and would remain so until some new philosopher's stone was found to convert gold back into iron--a much more difficult feat, it was thought. However, to be on the safe side, the English Parliament, in 1404, saw fit to pass an act declaring the making of gold and silver to be a felony. Nevertheless, in 1455, King Henry VI. granted permission to several "knights, citizens of London, chemists, and monks" to find the philosopher's stone, or elixir, that the crown might thus be enabled to pay off its debts. The monks and ecclesiastics were supposed to be most likely to discover the secret process, since "they were such good artists in transubstantiating bread and wine." In Germany the emperors Maximilian I., Rudolf II., and Frederick II. gave considerable attention to the search, and the example they set was followed by thousands of their subjects. It is said that some noblemen developed the unpleasant custom of inviting to their courts men who were reputed to have found the stone, and then imprisoning the poor alchemists until they had made a certain quantity of gold, stimulating their activity with tortures of the most atrocious kinds. Thus this danger of being imprisoned and held for ransom until some fabulous amount of gold should be made became the constant menace of the alchemist. It was useless for an alchemist to plead poverty once it was noised about that he had learned the secret. For how could such a man be poor when, with a piece of metal and a few grains of magic powder, he was able to provide himself with gold? It was, therefore, a reckless alchemist indeed who dared boast that he had made the coveted discovery. The fate of a certain indiscreet alchemist, supposed by many to have been Seton, a Scotchman, was not an uncommon one. Word having been brought to the elector of Saxony that this alchemist was in Dresden and boasting of his powers, the elector caused him to be arrested and imprisoned. Forty guards were stationed to see that he did not escape and that no one visited him save the elector himself. For some time the elector tried by argument and persuasion to penetrate his secret or to induce him to make a certain quantity of gold; but as Seton steadily refused, the rack was tried, and for several months he suffered torture, until finally, reduced to a mere skeleton, be was rescued by a rival candidate of the elector, a Pole named Michael Sendivogins, who drugged the guards. However, before Seton could be "persuaded" by his new captor, he died of his injuries. But Sendivogins was also ambitious in alchemy, and, since Seton was beyond his reach, he took the next best step and married his widow. From her, as the story goes, he received an ounce of black powder--the veritable philosopher's stone. With this he manufactured great quantities of gold, even inviting Emperor Rudolf II. to see him work the miracle. That monarch was so impressed that he caused a tablet to be inserted in the wall of the room in which he had seen the gold made. Sendivogins had learned discretion from the misfortune of Seton, so that he took the precaution of concealing most of the precious powder in a secret chamber of his carriage when he travelled, having only a small quantity carried by his steward in a gold box. In particularly dangerous places, he is said to have exchanged clothes with his coachman, making the servant take his place in the carriage while he mounted the box.

About the middle of the seventeenth century alchemy took such firm root in the religious field that it became the basis of the sect known as the Rosicrucians. The name was derived from the teaching of a German philosopher, Rosenkreutz, who, having been healed of a dangerous illness by an Arabian supposed to possess the philosopher's stone, returned home and gathered about him a chosen band of friends, to whom he imparted the secret. This sect came rapidly into prominence, and for a short time at least created a sensation in Europe, and at the time were credited with having "refined and spiritualized" alchemy. But by the end of the seventeenth century their number had dwindled to a mere handful, and henceforth they exerted little influence. Another and earlier religious sect was the Aureacrucians, founded by Jacob Bohme, a shoemaker, born in Prussia in 1575. According to his teachings the philosopher's stone could be discovered by a diligent search of the Old and the New Testaments, and more particularly the Apocalypse, which contained all the secrets of alchemy. This sect found quite a number of followers during the life of Bohme, but gradually died out after his death; not, however, until many of its members had been tortured for heresy, and one at least, Kuhlmann, of Moscow, burned as a sorcerer. The names of the different substances that at various times were thought to contain the large quantities of the "essence" during the many centuries of searching for it, form a list of practically all substances that were known, discovered, or invented during the period. Some believed that acids contained the substance; others sought it in minerals or in animal or vegetable products; while still others looked to find it among the distilled "spirits"--the alcoholic liquors and distilled products. On the introduction of alcohol by the Arabs that substance became of all-absorbing interest, and for a long time allured the alchemist into believing that through it they were soon to be rewarded. They rectified and refined it until "sometimes it was so strong that it broke the vessels containing it," but still it failed in its magic power. Later, brandy was substituted for it, and this in turn discarded for more recent discoveries. There were always, of course, two classes of alchemists: serious investigators whose honesty could not be questioned, and clever impostors whose legerdemain was probably largely responsible for the extended belief in the existence of the philosopher's stone. Sometimes an alchemist practised both, using the profits of his sleight-of-hand to procure the means of carrying on his serious alchemical researches. The impostures of some of these jugglers deceived even the most intelligent and learned men of the time, and so kept the flame of hope constantly burning. The age of cold investigation had not arrived, and it is easy to understand how an unscrupulous mediaeval Hermann or Kellar might completely deceive even the most intelligent and thoughtful scholars. In scoffing at the credulity of such an age, it should not be forgotten that the "Keely motor" was a late nineteenth-century illusion. But long before the belief in the philosopher's stone had died out, the methods of the legerdemain alchemist had been investigated and reported upon officially by bodies of men appointed to make such investigations, although it took several generations completely to overthrow a superstition that had been handed down through several thousand years. In April of 1772 Monsieur Geoffroy made a report to the Royal Academy of Sciences, at Paris, on the alchemic cheats principally of the sixteenth and seventeenth centuries. In this report he explains many of the seemingly marvellous feats of the unscrupulous alchemists. A very common form of deception was the use of a double-bottomed crucible. A copper or brass crucible was covered on the inside with a layer of wax, cleverly painted so as to resemble the ordinary metal. Between this layer of wax and the bottom of the crucible, however, was a layer of gold dust or silver. When the alchemist wished to demonstrate his power, he had but to place some mercury or whatever substance he chose in the crucible, heat it, throw in a grain or two of some mysterious powder, pronounce a few equally mysterious phrases to impress his audience, and, behold, a lump of precious metal would be found in the bottom of his pot. This was the favorite method of mediocre performers, but was, of course, easily detected. An equally successful but more difficult way was to insert surreptitiously a lump of metal into the mixture, using an ordinary crucible. This required great dexterity, but was facilitated by the use of many mysterious ceremonies on the part of the operator while performing, just as the modern vaudeville performer diverts the attention of the audience to his right hand while his left is engaged in the trick. Such ceremonies were not questioned, for it was the common belief that the whole process "lay in the spirit as much as in the substance," many, as we have seen, regarding the whole process as a divine manifestation. Sometimes a hollow rod was used for stirring the mixture in the crucible, this rod containing gold dust, and having the end plugged either with wax or soft metal that was easily melted. Again, pieces of lead were used which had been plugged with lumps of gold carefully covered over; and a very simple and impressive demonstration was making use of a nugget of gold that had been coated over with quicksilver and tarnished so as to resemble lead or some base metal. When this was thrown into acid the coating was removed by chemical action, leaving the shining metal in the bottom of the vessel. In order to perform some of these tricks, it is obvious that the alchemist must have been well supplied with gold, as some of them, when performing before a royal audience, gave the products to their visitors. But it was always a paying investment, for once his reputation was established the gold-maker found an endless variety of ways of turning his alleged knowledge to account, frequently amassing great wealth. Some of the cleverest of the charlatans often invited royal or other distinguished guests to bring with them iron nails to be turned into gold ones. They were transmuted in the alchemist's crucible before the eyes of the visitors, the juggler adroitly extracting the iron nail and inserting a gold one without detection. It mattered little if the converted gold nail differed in size and shape from the original, for this change in shape could be laid to the process of transmutation; and even the very critical were hardly likely to find fault with the exchange thus made. Furthermore, it was believed that gold possessed the property of changing its bulk under certain conditions, some of the more conservative alchemists maintaining that gold was only increased in bulk, not necessarily created, by certain forms of the magic stone. Thus a very proficient operator was thought to be able to increase a grain of gold into a pound of pure metal, while one less expert could only double, or possibly treble, its original weight. The actual number of useful discoveries resulting from the efforts of the alchemists is considerable, some of them of incalculable value. Roger Bacon, who lived in the thirteenth century, while devoting much of his time to alchemy, made such valuable discoveries as the theory, at least, of the telescope, and probably gunpowder. Of this latter we cannot be sure that the discovery was his own and that he had not learned of it through the source of old manuscripts. But it is not impossible nor improbable that he may have hit upon the mixture that makes the explosives while searching for the philosopher's stone in his laboratory. "Von Helmont, in the same pursuit, discoverd the properties of gas," says Mackay; "Geber made discoveries in chemistry, which were equally important; and Paracelsus, amid his perpetual visions of the transmutation of metals, found that mercury was a remedy for one of the most odious and excruciating of all the diseases that afflict humanity."' As we shall see a little farther on, alchemy finally evolved into modern chemistry, but not until it had passed through several important transitional stages.