FEEDING EXPERIMENTS WITH MIXTURES OF FOODSTUFFS IN UNUSUAL PROPORTIONS By Thomas B. Osborne and Lafayette B. Mendel 157 SOME PHYSICAL CHARACTERISTICS OF THE EAR............By John P. Minton 221 A METHOD FOR OBTAINING CONSTANTS FOR FORMULAS OF ORGANIC GROWTH. . . . . . By Simon Flexner and Harold L. Amoss 319 ANTHROPOLOGY CHRONOLOGY of the San Juan Area... By E. H. Morris 18 By A. V. Kidder and S. J. Guernsey 69 EDITORIAL BOARD The HOME SECRETARY and the FOREIGN SECRETARY of the ACADEMY The CHAIRMAN and the PERMANENT SECRETARY of the NATIONAL RESEARCH COUNCIL WILLIAM DUANE, '23 A. L. Day, '22 GANO DUNN, '22 J. M. CLARKE, '21 INFORMATION TO SUBSCRIBERS SUBSCRIPTIONS TO THE PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES at the rate of $5.00 per annum should be made payable to the National Academy of Sciences, and sent either to Easton, Pa., or to C. G. ABBOT, Home Secretary, National Academy of Sciences, Smithsonian Institution, Washington, D. C. Single numbers, $0.50. PAST publications of the NATIONAL ACADEMY OF SCIENCES are listed in these PROCEEDINGS, Volume III, pp. 743-753, December, 1917. In good part these publications are no longer available for distribution. Inquiries with regard to them should be addressed to the Home Secretary, National Academy of Sciences, Smithsonian Institution, Washington, D. C. PAST volumes of the PROCEEDINGS may be obtained at five dollars per volume unless the sale of the volume would break a complete set of Volumes I to V. Single numbers may be obtained for fifty cents except where the sale of such numbers would break up a complete volume. Only two hundred complete sets of the Proceedings are available for sale-Volumes I to VI, price $30.00. Orders should be sent to the Home Secretary, National Academy of Sciences, Smithsonian Institution, Washington, D. C. The following publications are issued by the NATIONAL RESEARCH COUNCIL. Orders and inquiries should be addressed: Publication Office, National Research Council, 1701 Massachusetts, Ave., Washington, D. C. (A) THE BULLETIN OF THE NATIONAL RESEARCH COUNCIL published at irregular intervals; Price $5.00 per volume of about 500 pages; individual numbers priced variously. (B) THE REPRINT AND CIRCUlar Series of THE NATIONAL, Research COUNCIL, individual numbers, variously priced. Communicated by G. E. Hale, November 10, 1920 One of the most interesting questions in astronomy concerns the relation of the spiral nebulae to the galactic system. Are they or are they not separate stellar systems comparable with our own? Especially during the last few years have many arguments been advanced both for and against. Real internal motions of the order indicated by the measures on Messier 101, communicated to these PROCEEDINGS in 1916,1 would raise a strong objection to the "island-universe" hypothesis. If comparable with our own system, spiral nebulae would be so distant that no ordinary velocities of their constituent parts would yield measurable displacements in the short interval of a few years. The measures on Messier 101 were, however, based principally on two plates taken by Mr. Ritchey at the 25-foot focus of the 60-inch reflector with an interval of only five years, and required confirmation before a general acceptance of the results could be expected. This was afforded in part by measures of three photographs of the same object taken at the Lick Observatory, which were kindly loaned by Director Campbell. Measures on Messier 81 also pointed in the same direction; while Lampland found analogous motions for Messier 51 in 1916, and Kostinsky3 in 1917. Meanwhile another five years has elapsed, which would have doubled the interval for the 60-inch reflector photographs of Messier 101; but, unfortunately, bad weather during the spring made it impossible to obtain a satisfactory plate. In August, 1920, however, Mr. Duncan secured a fairly good photograph of another spiral, Messier 33, for which an excellent plate, taken by Mr. Ritchey in 1910, was also available. Messier 33 is, moreover, better adapted for such measures than Messier 101, on account of its numerous condensations and their close approach to star 1 like appearance. For this same object two plates of short exposure, taken at the 80-foot focus of the 60-inch reflector in 1915 and 1920, were also available. Both these pairs of plates have been measured with the monocular arrangement of the Zeiss stereocomparator. It has been shown that with temperature properly controlled this instrument is admirably adapted to such measures, because it allows the bisection in quick succession of corresponding points on the two photographs; the possibility of not bisecting a nebulous and asymmetrical point in the same way on both plates is thereby greatly reduced, if not wholly avoided. A note on the unreliability of the stereocomparator for accurate measures has recently been published by Kreiken; but, as I have pointed out several times it is only necessary to keep the temperature of the room constant in order to secure good results with the Zeiss instrument. In our case the change in temperature during a series of measures can be kept within a few tenths of a degree. The influence of this variation is extremely small; but, as an extra precaution, we have adopted the plan of measuring the n points, first in the order 1......n, then in the order n. . . . . . 1. In this way practically all temperature effect can be eliminated, and it is easy to prove that the measures of the present series, which are of moderate length, cannot be affected by more than 10 or 12 per cent. For a series of several hundred points, whose measurement would take several days, the conditions are not so favorable, and in the present case it was thought best to await the completion of a new stereocomparator, now under construction in the instrument shop of the Observatory, in which the principal sources of trouble have been avoided, before undertaking the complete measurement of the plates. For a preliminary discussion, 24 comparison stars and 23 nebulous points were selected on the plates taken at the 25-foot focus. When the measures had been finished, Mr. Seares was kind enough to call my attention to some photographs of Messier 33 taken by him with and without color-screens. A few years ago Seares found that the outer points of spiral nebulae are decidedly blue in color. A rough comparison of his plates showed that I had been fortunate in the choice of both comparison stars and nebular points. Of the first only three are blue, while of the latter all but two are decidedly blue; these two points have been omitted in the following discussion, since they may not belong to the nebula. On the plates taken by me at the 80-foot focus all measurable points, a total of 89, were used. After the measures were finished I selected, with the help of the photographs taken by Mr. Ritchey and by Mr. Seares, 23 objects as comparison stars; these are all starlike in appearance and reddish in color. Ten points which are either very bright or very faint or for which the measures are uncertain were excluded. Of the remaining points, 22, including the centre, almost certainly belong to the nebula, |