496 



SCIENCE 



[Vol. LV, No. 1427 



still above, and should be able to determine with 

 certainty by these experiments whether the pene- 

 trating rays are of cosmic or of terrestrial origin. 

 While the instruments sent up weigh but 175 

 grams (6 ounces) they are capable of bringing 

 back a complete record of the temperatures, the 

 pressure, and the penetrating radiations existing 

 at all of the altitudes which thej' reach. These 

 altitudes should be about three times as great as 

 those ever obtained before in experiments of this 

 kind. These balloon flights will be reported later. 



On the measurement of a physical quantity 

 whose magnitude is influenced at random by pri- 

 mary causes beyond the control of the observer, 

 and on the method of determining the relation 

 betioeen two such quantities: Dk. Walter A. 

 Shewhakt, New York City. The objects of scien- 

 tific investigation are twofold, i. e., the determina- 

 tion of some form of average value and its prob- 

 able variation, and the determination of the rela- 

 tion existing between two or more such quantities. 

 In many problems of physical and engineering 

 science it is possible to assume that causes of 

 variation of the variable under consideration may 

 be controlled by the observer. Certain problems 

 in these sciences as in the fields of economies and 

 biology arise, however, wherein it is impossible to 

 control the causes of variation, and they must be 

 submitted to a statistical method of solution. An 

 outline of the necessary analysis is given and 

 illustrated. Application of the theorj- of correla- 

 tion and its physical interpretation was discussed. 



Ether-drift experiments at Mount Wilson in 

 1921 and at Cleveland in 1922: Professoe Day- 

 ton C. Miller, Case School of Applied Sciences, 

 Cleveland, Ohio. The Michelson-Morley experi- 

 ment to detect the relative motion of the earth 

 and ether was performed at Cleveland in 1887. 

 In explanation of the null result then obtained, 

 the Lorentz-FitzGerald effect was proposed. The 

 experiment was repeated by Morley and MiUer in 

 1904, with a much larger and more sensitive ap- 

 paratus, which was also especially arranged to 

 make a direct test of the Lorentz-FitzGerald 

 effect. Again a null result was obtained. The 

 suggestion was then made that the earth drags 

 the ether, and while there is no "drift" at the 

 surface of the earth, it might be perceptible at an 

 elevation above the general surface. The experi- 

 ment was again performed by the present author, 

 at the Mount Wilson Solar Observatory in March 

 and April, 1921, where the elevation is nearly 

 6,000 feet. The results indicated an effect such 

 as would be produced by a true ether-drift, of 

 about one tenth of the expected amount, but there 



was also present a periodic effect of half the fre- 

 quency which could not be explained. The inter- 

 ferometer had been mounted on a steel base and 

 in order to eliminate the possibility of magnetic 

 disturbance, a new apparatus with a concrete 

 base and with aluminum supports for the mirrors 

 was constructed. Observations were made in 

 November and December, 1921, the results being 

 substantially the same as in April. Before any 

 conclusions can be drawn, it is necessary to deter- 

 mine the cause of the unexplained disturbance. 

 The interferometer has again been mounted at 

 Case School of Applied Science, in Cleveland, and 

 observations are now in progress, the results of 

 which were reported in this paper, which was 

 illustrated by lantern slides and motion-pictures. 

 About 700 feet of motion-picture film was taken 

 at Mount Wilson by a member of the observatory 

 staff, showing the location and construction of the 

 apparatus and also the method of making the 

 observations. 



Some extensions in the mathematics of hydro- 

 mechanics: Dr. E. S. Woodward, Washington, 

 D. C. The most general specification of fluid 

 motion requires a minimum of twenty symbols, 

 or factors. Of these the most important are the 

 three velocity components, the three spin com- 

 ponents, and the four potentials from which the 

 velocity components are derived by differentiation. 

 The first part of the paper shows how it is more 

 advantageous, in general, to make use of the rela- 

 tions between the Laplacians, or the Laplacians 

 of the Laplacians, of these factors, than it is to 

 make use of the relations of a lower order. It is 

 shown that this extension greatly systematizes 

 and simplifies the statement and the solution of 

 problems on the motion of viscous fluids. The 

 second part of the paper refers to what the author 

 has ventured to call preharmonics, which are the 

 triple integrals of harmonic functions which figure 

 extensively in hydromechanics. It is shown how 

 to find all of the preharmonics corresponding to 

 all of the harmonic functions of positive and 

 negative integral degrees. 



Normal coordinates and Einstein space: O. D. 



BlEKHOFr. 



Algebraic solutions of Einstein's cosmological 

 equations: Edward Kasner. 



The geometry of paths: Oswald Veblen. 



Biographical memoir of Dr. J. A. Allen: F. M. 

 Chapman. 



Biographical memoir of Benjamin Apthorp 

 Gould: G. C. Comstock. 



Biographical memoir of Henry Ficlcering Bow- 

 ditch: W. B. Cannon. 



