the present plan, Dean A. R. Mann has the aid of three vice-officers as executives in the three main branches of the work of the college; resident instruction, extension, and research.

THE geological department of the New York State Museum will send into the field this year a considerable corps of workers for the purpose of collecting the fossil terrestrial plants of the Devonian Period. The collections of the museum are already very rich in such plant material, but it has all been acquired incidentally to the study of the fossil faunas of the state, and the reports of the museum have given inadequate attention to this important field. The physical conditions under which the Late Devonian deposits were laid down in New York were distinctly favorable to the accumulation of terrestrial plants in the shallow water offshore sands and shales, and it was said by Sir William Dawson that the state museum possessed a more extensive representation of this early land flora than was to be found elsewhere. The standing tree ferns found many years ago in the sands of Schoharie county and which are exhibited in the museum, are the oldest representatives of a terrestrial forest growing in place; the unique Archeosigillaria, 18 feet in length, is another extraordinary plant from this flora and these striking objects, supplemented by much unstudied material, give promise that the field may be opened to a more adequate knowledge of the first great land flora of the earth.

UNIVERSITY AND EDUCATIONAL
NEWS

DR. FREDERICK CHARLES HICKS, Sinton professor of economics, has been elected president of the University of Cincinnati, succeeding Dr. Charles W. Dabney, who retires on reaching the age of sixty-five. Dr. Hicks went to the University of Cincinnati in 1900 as head of the department of economics, having previously taught in the University of Michigan and the University of Missouri.

MR. HOMER P. LATIMER, professor of anatomy at the University of Nebraska, has been

granted leave of absence for the year 1920-21. He will spend this summer and next year in study at the Institute of Anatomy of the University of Minnesota. Mr. D. S. Brazda has been appointed instructor in anatomy to take charge of some of the classes during Professor Latimer's absence.

PROFESSOR S. ELIZABETH VON DUYNE, M.D., resident physician and professor of physiology and hygiene at Converse College, has resigned to accept a similar position at Goucher College, her alma mater.

DR. LINUS W. KLINE, formerly professor of psychology and education in the Duluth Normal School, who has been engaged in research at the Johns Hopkins University during the past year, has been appointed professor of psychology and education in Skidmore College.

DR. P. W. WHITING, in charge of biology at Franklin and Marshall College, Lancaster, Pa., has resigned to accept a position at St. Stephens' College, Annandale-on-Hudson, New York.

DR. RICHARD J. HARDING, McGill University, has been appointed professor of chemical pathology in the University of Toronto by the board of governors of the university.

DISCUSSION AND CORRESPONDENCE SCIENTIFIC WORK IN THE HAWAIIAN ISLANDS

HAVING recently returned from a tour of the Hawaiian Islands, and having familiarized myself with the scientific work that is being done there and which remains to be done in the Islands to the south, I am particularly interested in the success of the Congress so ably planned by Professor Herbert E. Gregory, of Yale University, who is now resident in Honolulu as director of the Bernice Pauahi Bishop Museum.

While the problems presented by the Islands are chiefly in geology, volcanology, and anthropology, there is also a great deal of interest in various fields of zoology and oceanography.

The cooperation planned by Professor

Gregory is designed to extend to the scientific men of New Zealand and Australia, and to take into consideration the larger work of the future, particularly as suggested by the vanishing anthropology of Polynesia. Unless this work is begun immediately and carried through with great energy and system, it will not be done at all. The material in physical anthropology is disappearing with almost incredible rapidity. The ravages of influenza during the past two years have swept away a large part of the members of the Polynesian race. The survivors on certain of the Islands constitute a very small percentage of the original population.

Scientific cooperation has begun through the special research in physical anthropology of the Hawaiian group established between the Bishop Museum and the American Museum of Natural History. Dr. Louis R. Sullivan of the American Museum staff has already left for the Islands and will make as complete a survey as possible of the pure and mixed Hawaiian races among the remnants. These results will be published in the Memoirs of the Bishop Museum. It is expected also that Curator Clark Wissler will represent the American Museum at the Pan-Pacific Scientific Congress in August.

HENRY FAIRFIELD OSBORN

THE ENERGY OF SMALL OSCILLATIONS TO THE EDITOR OF SCIENCE: The well-known theorem that in any linear harmonic oscillation the total energy is, on the average, half kinetic and half potential is so important in many fields that perhaps the following very simple and elementary proof will be of general interest. It can hardly be new, it is so simple and obvious, but at any rate it is not common, for it does not appear in any of the best known treatments which have been consulted.

Consider a particle of mass m which is displaced from its equilibrium position a distance x, and is vibrating in a circle. Then, as is well known, the kinetic energy is equal to the potential energy. For let the elastic restoring force be given by kx. We must

then have kx = mv2/x for steady motion. The potential energy of the particle when at a distance x from the equilibrium position is equal to the work done in displacing it this distance, which equals the distance times the average force, which equals 1/2(kx) x. Substituting the above value of kr we have for the potential energy 1/2mv2, and the proposition as stated is established. But any such circular vibration may be thought of as composed of two exactly similar linear harmonic oscillations. (When considering energy the phase difference and direction of oscillation is obviously irrelevant.) Therefore we must associate, on the average, half of the total kinetic and half of the total potential energy of the circular vibration with each of the linear vibrations. Since these are equal in the case of the circular vibration they must also be equal in the case of the linear vibration. The result is obviously perfectly general for any linear harmonic oscillation. WARREN WEAVER CALIFORNIA INSTITUTE OF TECHNOLOGY

CARBON DIOXIDE AND INCREASED CROP

PRODUCTION

TO THE EDITOR OF SCIENCE: Should one infer from Mr. Harrow's note in the latest issue of SCIENCE (May 7, 1920) that the question of "fertilizing" with carbon dioxide were not known to plant-physiologists and agricultural chemists in this country?

If so, it might be worth while to mention that for a number of years, at least for the last ten years, this topic has been the subject of many experiments in Europe, especially in Germany.

The botanists, Hugo Fischer and Adolf Hansen among others, have contributed much to its study. It has even found its place in modern German text-books of plant physiology -for instance in Molisch's "Pflanzenphysiologie"-and no doubt, also in those of agricultural chemistry, such as Schneidewind's "Ernährung der landwirtschaftlichen Kulturpflanzen."

M. W. SENSTIUS

VACANCIES In the grade OF ASSISTANT

CIVIL ENGINEER, U. S. NAVY

APPICATIONS are being received at the Bureau of Yards and Docks, Navy Department, Washington, D. C., to fill 30 vacancies, more or less, in the commissioned grade of assistant civil engineer, U. S. Navy, with the rank of lieutenant (junior grade). The pay and allowances at entrance are approximately $3,200 per annum, with increases up to $9,000, depending upon length of service and promotions.

The candidate must be an American citizen, between the ages of 21 and 34 years on August 1, 1920; must have received a degree in engineering from a college or university of recognized standing; must have had not less than 12 months' practical professional experience since graduation, and must be of good moral character and repute.

The preliminary examination to determine general fitness will be based on papers submitted by the candidates, reaching the Board on or before August 23, 1920, covering college record, testimonials, references and professional experience. The candidate is not required to report in person for the preliminary examination. Physical examination by a board of medical examiners will be made of those candidates who qualify in the preliminary examination.

Those who qualify in the preliminary and physical examinations will take the final oral and written examinations to be held in Washington, D. C., as soon as possible after the preliminary examination papers have been passed on by the Board.

Officers of the Corps of Civil Engineers are detailed principally to the various navy yards and naval stations to supervise the work under the Bureau of Yards and Docks, Navy Department, Washington, D. C., consisting of the design and construction of all the public works of the naval establishment on shore as well as the maintenance and repair of existing structures. The work is exceptionally varied and offers an attractive field for able and ambitious young engineers. C. W. PARKS, Chief of Bureau

ARISTOTLE AND GALILEO ON FALLING BODIES

A DRAMATIC event in the history of physics is Galileo's dropping a one pound shot and a hundred pound shot together from the leaning tower of Pisa, to disprove Aristotle's law of falling bodies. In 1913 Professor H. H. Turner of Oxford, in a lecture at the Royal Institution, quoted Galileo's version of Aristotle's law:

Aristotle said that a weight of ten pounds, for example, fell ten times as fast as a weight of one pound.1

To this J. H. Hardcastle replied, "Aristotle never said this at all"; he refers any one who "wishes to find out for himself" to Aristotle's "Physica," Book IV., cap. 8. He does not quote from Aristotle, but quotes from Thomas Aquinas's commentary on the passage in Aristotle to which this reference points. Accepting Hardcastle's statement, G. Greenhill, William Ramsay and Oliver Lodge arrive at the conclusion3 that Aristotle has been misunderstood. Greenhill interprets Aristotle as teaching "that the terminal velocity of a body in a medium is proportional to the weight," a law "justified by Newton in his experiments in St. Paul's "4 and exemplified in the motion of "a raindrop or hailstone falling vertically in the air, or of a smoke particle up the chimney"; Galileo discussed an altogether different question, viz., "the start of such a body from rest." Ramsay refers to Ostwald as pointing out that "Aristotle was much more impressed with the retarding effect on the velocity of the mass of the medium through which the falling mass fell, than with the laws of 'free fall.'" Lodge emphasizes "the fact that 'terminal velocity' is the best instance of Newton's first law of motion in actual operation."

These remarks are interesting, but not altogether to the point. Those modern apologists do not actually quote Aristotle, nor do they base their reasoning on what Aristotle actually said.

Aristotle discusses falling bodies in six or more different parts of his "Physica" and "De Cœlo."

1. He considers a body falling through media of different densities-air, water and media indefinitely rare. Then he considers also bodies of different weights falling through the same medium. Endeavoring to disprove the existence of a vacuum, Aristotle says:

That which is heavier. . other things being equal, moves faster through the same space, and indeed faster according to the ratio of the magnitudes of the things, so that this must happen also through a vacuum. But this is impossible; for why should it move faster? In a plenum this is necessarily true, because the larger moves more rapidly by its power of greater penetration.

Thus, according to this Aristotelian passage, not only do the larger bodies move faster through a medium, but they would move faster even through a vacuum, if such existed.

2. Aristotle asserts that each of the bodies constituting the universe was originally at rest (as taught by Anaxagoras), that each was heavy or light and had power to move.

For suppose 4 without weight, but B possessing weight; and let A pass over a space CD, but B in the same time passes over a space CE-for that which has weight will be carried through the larger space. If now the heavy body be divided in the proportion that space CE bears to CD, . . . and if the whole is carried through the whole space CE, then it must be that a part in the same time would be carried through CD. Consequently the body without weight and the one possessing weight pass over the same distance, which is impossible.

Here Aristotle's law is applied to bodies initially at rest.

5 ́ ́Physica,” Book IV., cap. 8. We are using Carl Prantl's "Aristoteles' Werke. Griechisch und Deutsch,'' Bd. I., Leipzig, 1854, pp. 187-191.

"De Cœlo," Book III., cap. 2; Prantl, Vol. 2, pp. 203-205.

3. Aristotle argues that "if there were an unlimited increase in the weight, there would be also an unlimited increase in velocity." The volume of a falling body is specially considered in "De Cœlo," Book IV., cap. 1:8

4. In "De Cœlo," Book I., cap 6, we find:

If such and such a weight is moved so and so far in such and such a time, then some larger weight will be moved through the same distance in still shorter time, shorter in the inverse ratio of the weights. A limited weight can pass over any limited line in a limited time.

5. In "De Cœlo," Book IV., cap. 2,10 Aristotle argues, likewise, that the more fire will proportionally move upward with greater speed and the less fire with less speed, and similarly for the downward motion of more gold or more lead. Here, as in most other passages, the shapes of the moving bodies are not considered.

The above shows that Aristotle considered his law applicable when the motion took place from rest as in (2), when there was no upper limit to the weight that the moving body may have as in (3), when the time of motion may be reduced or increased as in (4), and when the moving bodies are different weights of any metal, like gold or lead, as in (5). No restriction is placed by Aristotle to the combination of some or all of these four conditions in one and the same motion. To our surprise, he was willing to apply his law even to motion in a vacuum (were a vacuum possible) as is seen in (1). It appears there fore that Aristotle allowed his law a generality of application which certainly did include the special conditions under which Galileo performed his experiment of dropping a onepound shot and a hundred-pound shot through the air from the leaning tower.

UNIVERSITY OF CALIFORNIA

FLORIAN CAJORI

7"De Cœlo," Book I., cap. 8; Prantl, Vol. 2,

p. 65.

That body is heavier than another which, in an ●qual bulk, moves downward quicker.

8 Prantl, Vol. 2, p. 243. Prantl, Vol. 2, p. 47.

10 Prantl, Vol. 2, p. 249.

SPECIAL ARTICLES

AN ACCURATELY CONTROLLABLE MICRO

PIPETTE

A NUMBER of pipette devices have been employed for the injection or extraction of minute quantities, which have served their purpose quite satisfactorily. Among these may be mentioned the several methods described by Toldt, Barber2 and Chambers. However, in certain recent work I was unable to use with the necessary accuracy any of these methods and so undertook to construct a micropipette which could be very reliably and precisely controlled.

The simple apparatus now being used serves my needs so surprisingly well that I offer this description of it hopeful that the method will

quantities of various solutions into the cytoplasm and macronucleus and have induced the formation of vacuoles near the contractile vacuole in such manner as to obtain significant data on the behavior and function of the latter structure. An account of these results will be published in later papers; I shall here only describe the method employed. I am indebted to Professor S. O. Mast for several important suggestions in the construction of the apparatus.

The general principle involved in the operation of this mechanism is the inducement at will either of large or of very delicate changes in a given volume of mercury by means of a small steel needle attached to a finely threaded thumb-screw.

be of service to others. By its use I have succeeded in extracting the micronucleus from the ciliate Euplotes, have injected very minute

1 Toldt, "Die Injection unter messbarem Drucke," Archiv. f. Mikr. Anat., 1869, 5, 167, Taf. XI.

2 Barber, M. A., "The Pipette Method in the Isolation of Single Microorganisms and in the Inoculation of Substances into Living Cells," The Philippine Jour. Sci., Sec. B, Trop. Med., 9, 307. 3 Chambers, R., "The Microvivisection Method," Biol. Bull., 1918, 34, 121.