answer we have only to point to the flight of the vultures, which, unlike the sea birds, fly high and may maintain their course uninterruptedly into a high wind at great altitudes. Nor need we, in fact, look away from the sea birds for an evidence to show that wind breaks, although often utilized by the bird, offer no satisfactory solution of the problem. Quite recently I spent some time in watching the flight of two gulls on the Potomac River. A stiff breeze was blowing, but the waves which it produced were scarcely 12 inches high-entirely too small to be effective as wind breaks-while the broad expanse of water, the level nature of the surrounding country, and the direction from which the wind came precluded any assumption of a general rising current of the air. Considered in its entire mass, there is every reason to believe that the wind was horizontal. In this horizontal wind, by rising to a height of about 40 feet the gulls were able to soar with the utmost ease, sailing steadily into the wind or across it without loss of elevation and without flapping. This and similar occurrences go to show that a strong horizontal wind, though not, so far as we have any evidence, a homogeneous one, suffices for sustained soaring flight. Only the small and rapid changes in the direction of the actual wind, whose course, in general, is horizontal, are here supposed to become effective in sustaining the bird. However, in his work on The Internal Work of the Wind, Mr. Langley, while including under this title the energy arising from all changes in the condition of the wind, whether in velocity or direction, applies the theory more particularly to a consideration of the available power resulting from changes in the velocity. In addition, then, to the energy obtained from the winds in the manner just described, there must be considered that which arises from the latter source, and all these variations taken together constitute, in their effect upon resisting bodies, the internal work of the wind. We have finally to consider flight in winds of moderate velocity. Looking again to the birds for the facts from which to reason, we find in such winds they still soar, but in a manner which is neither that adopted in feeble winds nor in strong ones, but intermediate in character. In moderate winds the bird avails himself of the power found in ascending currents and also in the internal movements of the wind. In light winds it rises only by soaring in circles; in heavy winds this method may be, and usually is, wholly discarded, the flight becoming sustained and direct; while in moderate winds it is still under the necessity of rising in circles, but less frequently than when the winds are light, and while sustained flight in direct courses is no longer possible as in the case of high winds, it yet obtains from the winds a certain amount of uplift which renders its rate of descent less rapid than it would be in a calm or in light winds. Observation abundantly shows that in direct flight the rate of descent is indirectly proportional to the velocity of the wind. Thus if a bird in a calm descends at the rate of 3 feet per second, the rate of descent will be reduced to 2 feet per second in a wind of a certain velocity, to 1 foot per second as the velocity becomes greater, while for a sufficiently high velocity there will be no descent at all, and as the velocity still further increases the bird may ascend where before it had been descending. In direct flight in a calm the black vulture will be found to maintain his elevation only by flapping its wings one-third of the time; in a light wind it will flap less frequently; in a moderate wind still less frequently; while in a high wind it will cease flapping entirely. The supporting power of the wind thus varies not only as its velocity relative to the bird, but also as its absolute velocity. In moderate winds, therefore, the bird, if it does not flap, can only increase its altitude by soaring in circles, but in direct flight its descent is less rapid than in light winds, and it can consequently sail further and need not so frequently resort to spiral flight. But as an ascending column of air can not maintain a fixed locality, but must be carried forward with the wind, the bird, if it utilizes such currents, must also drift with the wind. This it will almost invariably be found doing when the winds are light or moderate. Thus if it be advancing into a wind it will turn upon its course and drift with it whenever it attempts to rise by soaring in circles. The bird may, of course, in high winds circle without drifting, as there is then no necessity for utilizing ascending currents, and we find in this fact a complete refutation of the supposition that ascending currents depend for their maintenance upon wind-breaks, since wind-breaks can not move across the country as ascending currents do. As some writers have seemingly regarded the effect of wind-breaks as an important factor in the problem of flight, I may state on the authority of Professor Ridgway that on the level, treeless prairies of the West, where no wind-breaks occur, the birds soar as perfectly as in regions where wind-breaks are of common occurrence. My own observation has been that the birds habitually take advantage of existing wind-breaks, such as hill slopes, ridges, buildings, and railroad embankments, as they may often be seen following the crest of a ridge upon the windward side for long distances, but that when every allowance has been made for their possible influence the problem of flight in its essential features remains unchanged when this factor has been taken out. What I have said seems in general to be corroborated by the obser vations of M. Mouillard, who says of the great tawny vulture: "If the wind be feeble he can climb into the air by circling round and drifting back somewhat. If the wind be brisk enough to sustain him thoroughly he can rise perpendicularly, facing the wind, without wheeling round, and even advance into the wind while rising. This unlimited advance against the wind current without beat of wing, without apparent effort, and almost without act of guidance, is performed every day by myriads of winged creatures; and if the reader doubts the fact he can thoroughly satisfy himself by a trip to the trade-wind latitudes." Unquestionably the problem presented by the soaring birds is a difficult one, as the air in which the bird moves is invisible, our knowledge of its movements is limited, and the bird himself must be studied from a distance. No solution amounting to a demonstration can at present, therefore, be looked for. Nevertheless, some sort of a solution is desirable if only to give direction to our investigations, and the proposed solution here given of flight in light winds, if it should prove to be the correct one, opens up possibilities of artificial flight which can scarcely be overestimated, for the sources of power which enable the bird to fly with so little expenditure of its energies are all perhaps equally available for man in artificial flight, since the maneuver of flying in circles is very simple and is one which could be easily reproduced. THE REVIVAL OF ALCHEMY.' By H. CARRINGTON BOLTON, Ph. D. "Superfluous rehearsalls I lay asyde, operatyon; That by my wrytyng who so will guyded be, Of hys intente perfyctly speed thall he." GEORGE RIPLEY (1471). Fraud, folly, and failure have been deeply written into the annals of alchemy in all ages. It was early characterized as an "art without art, beginning with deceit, continued by labor, and ending in poverty," and in modern times its extravagant pretensions have been condemned by an exact and critical science; yet notwithstanding there are to-day indications of a resuscitation of the captivating theories and of renewed attempts at their practical application, of great interest to students of the intellectual vagaries of mankind. Belief in the possibility of prolonging life by an artificial elixir and of transmuting base metals into silver and gold was generally entertained in the Middle Ages, not only by the ignorant masses, but even by serious-minded philosophers imbued with all the learning of the time; and the popular faith was sustained by the tricks of unprincipled imposters who found it profitable to prey upon the credulity and avarice of their fellow-men. Those who in modern times have written of alchemists find in the extravagant views of a Paracelsus, and in the careers of a Flamel, a Sendivogius, or of a John Dee more entertaining materials than in the abstract conceptions of sober philosophers, and consequently most readers are more familiar with the misdeeds of adventurers than with the honest beliefs of respectable men of science. Before condemning those who labored day and night to solve the prob lems of transmutation and the elixir of life, we should consider their intellectual environment. Superstitious beliefs of every kind prevailed; even the sciences were in bondage; astronomy was dominated by Read before the New York Section of the American Chemical Society, October 1, 1897. Reprinted from Science, N. S., Vol. VI, No. 154, pages 853-863, December 10, 1897. astrology; medicine was influenced by magic; natural history was subject to blind belief in authorities, and scientific chemistry was entirely overwhelmed by the chimeras of alchemy. Kepler and Tycho Brahe, at the court of Rudolph II did not think it beneath their dignity to cast horoscopes for gain and to predict the future by consulting the positions of celestial bodies, even while formulating the laws governing their motions. European crowned heads retained astrologers and alchemists as members of their courts. A century later Sir Isaac Newton dabbled with furnaces and chemicals in true hermetic style; and Leibnitz showed the courage of his convictions by acting as secretary of an alchemical society in Germany. The influence of superstition on the mental attitude of truly great men decreased with the advancement of learning, and when the foundations of scientific chemistry were laid by Priestley, Lavoisier, Scheele, and their contemporaries the doctrines of alchemy were abandoned. And yet not wholly abandoned, for there seems to have been a small number of persons in all countries who have clung to the hope of realizing transmutation, a hope sustained by the desire to reap the golden reward. This minority rejected the extravagant belief in a life-prolonging elixir, and in the divine origin of the profound secrets of the initiated, and sought to appropriate from the growing sciences such discoveries and theories as could be interpreted in favor of transmutation. The printing press has never ceased to issue works devoted to the subject. Some authors have written of a "higher chemistry," and others have sought to reconcile the new doctrines of chemists with the ancient theories of alchemists. As recently as 1832 a German professor wrote a learned volume with the avowed intent of proving the verity of transmutation from historical sources (Schmieder's Geschichte der Alchemie, Halle, 1832). The number of reprints of the grotesque writings of reputed adepts which have appeared since chemistry has become an exact science is surprisingly large, and the fact that they find purchasers indicates a small but zealous class of hermetic students. So eminent a chemist as Sir Humphrey Davy did not hesitate to affirm that some of the doctrines of alchemy are not unphilosophical. Recent discoveries in physics, chemistry, and psychology have given the disciples of Hermes renewed hopes, and the present position of chemical philosophy has given the fundamental doctrine of alchemy a substantial impetus. The favorite theory of a prima materia, or primary matter, the basis of all the elementary bodies, has received new support by the discoveries of allotropism of the elements, isomerism of organic compounds, the revelations of the spectroscope, the practical demonstrations by Norman Lockyer, the experiments on the specific heat of gaseous bodies at a high temperature by Mallard and Le Châtelier, the discoveries of Sir William Crookes (as set forth in his monograph on Meta-elements), the discovery by Carey Lea of several singular allo |