periodically at the depressions but not at the ridges, then for a constant speed of the car body forward over the road, and thus presumably of the axle also (neglecting any vibration lengthwise of the road, of the wheels relative to the body) a constant rate of rotation of the wheels would be consistent with this explanation. For in ascending and descending the ridges the periphery of the tire at the point of contact would be moving at an angle with the direction of the forward motion of the axle, and if there were no slipping anywhere, would have to be moving circumferentially around the axle at a rate greater than that necessary in the depressions. But by the same argument there would be a tendency to spin on the peaks of the ridges also, which would tend to wear them down. This explanation by slippage uses, to be sure, the natural rate of vibration of the wheels relative to the approximately stationary body of the automobile. But on its face it does not appear so acceptable as that attributing the ridges entirely, or almost so, to the simple, periodic bumping of the road by the wheels, with negligible periodic slip. The problem more generally, and in its simplest form, is that of a vibrating system of two masses, one much greater than the other, connected by an elastic spring, and affected by an elastic push corresponding to that of the rubber tire, and by gravity. As to the transverse growth of the ridges, whose individual identity as they lie across the road, can be recognized often over a length of ten or twelve feet, possibly more, suppose a second car, similar to the first, follows it and strikes the first humps formed, which will be necessarily short transversely to the road. The chances are that the wheel of the second car will not strike the humps squarely if at all, but at one end of them or the other. But this is sufficient to give an initial bounce, and the result is a slight lengthening, transverse to the road, of the initial humps. It is rather remarkable that the two series of humps, one at either side of the first car to pass, should eventually join up into continuous ridges across the road, but this is the actual effect from the passing of many cars. Perhaps this joining up is the result mainly of a sympathetic action, mentioned above, of the wheel on the opposite side of the machine. Alternate grooves and ridges, roughly parallel, can be formed by water flowing across the road, but this type is likely to lie obliquely rather than perpendicularly with respect to the road, and at any rate will hardly be so uniformly spaced over a considerable distance. The opinion may be ventured that where ridges of the particular washboard type are found on solid road surface devoid of loose material, they were formed by the vibration process at a time when the ground, due probably to moisture, was in a more pliable condition. The frequency of vibration of the wheels of a car relative to a stationary body is a quantity much greater than the frequency of the heavier body relative to stationary wheels. Assuming one and one half feet as the approximately uniform interval between the ridges of the "washboard," and further assuming 30 miles per hour as the speed of the "average" car, the average vibration rate of the wheels relative to the body of the car, comes out about 30 v.p.s. (v=λ. The value of one and one half feet as the distance between ridges in a group makes the vibration rate about 2 per cent. less than the speed of the automobile in miles per hour.) A certain driver, who has driven much on these desert roads, mentioned 25 miles as an average value for all machines, which would give approximately 25 v.p.s. for an average value. The question might be raised whether the "average" car, or a particular class of cars, heavy or light, is in the main responsible for the ridges. Also, is the vibration chiefly that of the balloon tires? Heavier cars with balloon tires were observed to travel in the straight stretches at 40 miles and better. Riders in the heavier machines traveling at the higher speeds are probably little disturbed by these corrugations on the road. The bumping effect in a lighter car at a speed of 12 or 15 miles would become at times monotonous, to say the least. A certain other driver living in the desert stated he found the bumping effect least at a speed of about 35 miles. This should vary with the type of automobile, but theoretically for each car there is one best speed for maximum comfort of riding, and that is the speed at which the wheels "resonate" with the ridges. The writer has taken no actual measurements on these ridges. Moreover, it would be interesting to check the vibration rates of automobile wheels in the laboratory, with the values calculated on the basis of the physical explanation offered. Such matters are properly subjects for consideration in the fields of road and automobile engineering. DEPARTMENT OF PHYSICS, UNIVERSITY OF CALIFORNIA AT LOS ANGELES, CALIF. L. E. DODD THE REVERSIBLE MIXING OF SUBSTANCES IN THE CONDENSED STATE AT THE ABSOLUTE ZERO OF TEMPERATURE THE thermodynamical results established in a previous paper1 and extended in a subsequent paper2 1 Read at the Philadelphia meeting of the American Association; SCIENCE, Feb. 25. where T denotes absolute temperature. Hence if hm can be expanded in powers of T by Taylor's Theorem hm = aT3 near the absolute zero of temperature, where a is a constant. This result could be investigated experimentally without great difficulty. It would involve measurements of the change in temperature on mixing a number of substances near the absolute zero of temperature, and a determination of the corresponding specific heats of the substances and the resultant mixture. The quantities Hm and A are shown to possess similar properties, where Hm denotes the heat absorbed on reversibly mixing the substances and A the maximum work done during the process. In the first paper on the subject it was shown that the controllable internal energy and entropy, which are functions of the controllable variables v and T, are zero for any substance or mixture in the condensed state under their vapor pressures at the absolute zero of temperature. If several substances are simultaneously considered another controllable operation becomes possible, namely that of mixing some of them. From the way the foregoing result was established it does not follow directly that there will be no change in internal energy or entropy on mixing the substances under their vapor pressures at the absolute zero of temperature. It is now shown that no change takes place. With this result as basis it is further shown that the well-known formulae DOUBLE COVEY OF CALIFORNIA VALLEY QUAIL It is common knowledge that the males of many species of birds assist in the protection and care of the young birds. During the week of June 12-18, the following interesting observations were made by Mr. R. A. Holley, of Fillmore, California, on what was apparently a double covey of California Valley quail or partridge (Lophortyx californicus vallicola (Ridgw.)). In the early part of the week he flushed a large flock of quail in an orchard. The covey consisted of twenty-three young quail of two distinct sizes and two adult males, one of which had a crippled leg, but no adult females. Approximately one half of the young quail were about one third grown, the rest were of uniform size but somewhat larger. The following day the same covey was seen again. The crippled male was acting as sentinel while the other male was feeding with the young ones. When the sentinel was approached the covey flew a short distance away. It was then noted that the crippled male had taken his place with the young on the ground and that the other male was acting as the sentinel from the fence post. This same covey of two males, one a cripple, and the twenty-three young belonging to two size groups were seen on four successive days in the same orchard. Apparently the females of the two adult pairs had been killed and the two males with their respective broods had joined forces. This alliance had made it possible for the males to alternate as sentinels and warn the combined broods of any impending danger. ZOOLOGICAL DEPARTMENT, OCCIDENTAL COLLEGE, LOS ANGELES, CALIF. R. M. SELLE SCIENTIFIC BOOKS Man not a Machine. By E. RIGNANO. London. Kegan Paul, French, Trubner & Co., 1926. 77 pp. In this handy little volume Rignano discusses in a brief but suggestive way the mechanistic and the vitalistic interpretations of life, especially of the life of man. The subject matter is considered under nine heads, such as metabolism, adaptation, behavior, instincts, mentality, social relations, and the like. The author concludes that in all nine aspects there is an irreducible residuum that can not be explained away on mechanistic grounds. This irreducible element, always present, is of a purposive character. Having thus shown the insufficiency of the mechanistic interpretation, Rignano concludes that a vitalistic interpretation of life is the only one tenable. To the reviewer this step seems to be a non sequitur, for in addition to vitalism and mechanism there are other possible ways of considering life, witness that embodied in emergent evolution. Thus the view of life from the standpoint of emergent evolution avoids the obvious limitations of the mechanistic conception and yet differs radically from vitalism. It may be, therefore, a much more truthful interpretation of life than either vitalism or mechanism. It is to be regretted that this aspect of the subject has not been discussed by Rignano, whose book, however, affords good reading, suggestive and stimulating. G. H. PARKER Traité de Geographie Physique par EMMANUEL DE MURTONNE, professeur à la Sorbonne. Tome troisième: Biographie (en collaboration avec A. CHEVALIER ET L. CUÉNOT) Un Vol. in 8°, 464 pages, 94 figures dans le texte, 24 photographies hors texte. Librairie Armand Colin, Paris. THE first edition of the "Traité de Geographie Physique" appeared twenty years ago and a second edition later. The author has remodeled his work, which has now been published in a third edition. Volume III devoted to biogeography completes the work, and in it there are 404 pages of text, instead of 154 pages in the first edition, 94 figures in place of 62, and 25 pages of bibliography instead of 10 pages. The growing complexity of the subject, and the abundance of technical studies devoted to biogeography have been such as to necessitate the association of two other scientists: MM. Chevalier, director of the laboratory of colonial agronomy, and Cuénot, professor of zoology in the University of Nancy. The volume is a single complete treatise on biogeography and is based on current and recently pursued research on the subject. A chapter is devoted to general principles, as common to botanical and zoological geography. Five chapters are devoted to phytogeography. One of them deals with the science of the soil, another to plant sociology, where are given in a detailed manner the most recent investigation of plant associations at A by a cone of fiber paper, and at the point D by fiber board. The lower end and the outer wall of the drum are brightened to make contact with B and C. Then a band of fiber paper F is held in place around the drum by two rubber bands R. Seven triangular pieces are cut from this band of fiber paper as shown in figure 1, to allow the point B to make contact with the drum. When this point comes in contact with the drum, the magnetic switch, No. 2829653Z2 General Electric, M closes the power circuit P, and the lights are on. As the point B runs onto the fiber paper breaking the control circuit the magnet is demagnetized, and the lights are turned off. pended in a liquid of density 1.0 and located 20 cm. from the center of the centrifuge. Let the viscosity be 0.01 (water at 20° C.) and the speed be 3,600 r.p.m. (P=60). Then: v= 8(5 x 10-) x 20 x 602(1.1-1.0) = 158 x 10-o cm./sec. or 0.57 cm./hr. This velocity is certainly not great, since under the conditions stated some 8.8 hours of centrifuging would be necessary to carry a particle 5 cm. And if analysis is made of the values used in this problem it will be seen that they are taken to give v a probable maximum value. The viscosity in practice is ordinarily greater than that of water, and the radius of the particle is almost unquestionably less than 5×10-6 cm. Ordinarily centrifuge methods applied to filterable viruses are from the standpoint of physical laws of questionable value. The surface-volume relationship in the illustration problem is such that a 1 cc. volume would have to be contained in a film less than a micron thick and over half a meter square to give relatively the surface exposure, considering both sides of the film. Or a centimeter cube with its 6 cm.2 surface would have to have a density about 1/100 that of air to give the same surface-mass relationship as pertains to the minute particle described. Thanks are due to Mr. W. W. Sleator of the laboratory of physics of the University of Michigan for checking and correcting this problem. M. S. MARSHALL, Research Bacteriologist MICHIGAN DEPARTMENT OF HEALTH PERSIMMON SEEDS FOR CLASS USE AN examination of the seeds of the common persimmon, Diospyros virginiana, convinced the writer that they should make excellent class material for embryological studies as well as for studies of the structures of a thick-walled endosperm. The comparatively large, straight embryo is easily removed from the endosperm and its parts are easily seen. Younger stages should make good microscopic preparations for embryological work, provided that the difficulties encountered in cutting the testa and endosperm are not too great. Carbohydrate is apparently stored in the thick cell walls of the endosperm in the form of cellulose or hemi-cellulose, and this being the case, the germinating seeds should be a good source of cytase-like enzymes. During the past season the writer sent a supply of persimmon seeds to Dr. E. M. Gilbert, of the department of botany of the University of Wisconsin, who writes that they have been used successfully in SPECIAL ARTICLES THE OCCURRENCE OF THE PLATINUM RECENTLY I have had the opportunity of studying the results of some forty analyses of the Canyon Diablo meteorite, both of the iron and of the socalled shale-balls. The latter appear to be merely the oxidized iron, as some of them still have an unoxidized iron core. The analyses were made by at least eight different analysts, including Dr. J. W. Mallet, H. H. Alexander, A. H. Phillips, G. H. Clevenger and myself, and included the content in platinum, iridium and in some cases palladium. There have been but two references in literature to the occurrence of platinum in meteorites.1 Trottarelli reported palladium in the Collescipoli stone, and J. M. Davidson found the Coahuila iron to contain 39 parts per million of platinum and 2.44 parts iridium. In the Toluca meteorite sufficient platinum was found to give a precipitate of potassium chloroplatinate, which from its color probably contained iridium. No quantitative estimation was made. The Canyon Diablo analyses, weighted according to my best judgment, average as follows: The ratio of platinum to iron in the shale-balls corresponds closely to that in the unoxidized meteorite, the ratio of iridium to iron is lower and that of palladium to iron somewhat higher. The average amount of nickel found in all the analyses, not weighted, is 6.44 per cent. Clarke gives the average nickel for 318 meteorites as 8.52 per cent., and in the Ovifak iron 2.95 per cent. It may be considered probable that platinum, and doubtless all the platinum metals, would be found in • all meteorites if analyses were made with this end in view, though the estimation of three or four tenths of an ounce of platinum and iridium to the ton of meteoric iron is no simple task. It may be noted 1 Trottarelli: Gazz. chim. ital. 20 (1890), 611; Davidson: Amer. J. Sci. (4), 7 (1899), 4. that in dissolving the iron in either sulfuric or in hydrochloric acid, some of the platinum and iridium will go into solution, and this doubtless accounts for the varying results on the Canyon Diablo iron where such a method has been used. Attention has been called by many observers to the association of the metals of the eighth group in nature. In 1891 Daubrée and Meunier noted the occurrence of metallic iron containing traces of platinum in the gold washings of Berazovsk in the Ural, and also that many meteorites resembled rocks with which platinum is generally associated in nature. It may be worth while to attempt a rough approximation of the relative amount of the metals of the eighth group, assuming that the iron of the interior of the earth contains the same proportion of the platinum metals as the Canyon Diablo meteorite. For this we can use the calculation of F. W. Clarke for the earth as a whole: The An approximation of the amount of iridosmium compared with platinum can be made from the amount produced over a long period of years. present proportion (1925) of 9 per cent. as much iridosmium as platinum is obviously too large, owing to the stimulation of production by the abnormally high price of iridium, while the earlier production of 1 per cent. to 3 per cent. is as obviously low, from the slight market demand for iridosmium and the metals obtained from it. We may fairly assume 5 per cent. as about the proper proportion of iridosmium to platinum. On this basis, our figures for 2 Afr. Mining Eng. J. 38 (1927), 123. |