June 22, 1900.] 



SGIENGE. 



989 



methods, and the application of digestion co- 

 efficients in practice. 



The compilation represents a large amount of 

 painstaking work and study on the part of its 

 authors, but it was well worth the undertaking 

 and will prove a valuable summary. It will 

 make it possible to use American digestion co- 

 efficients quite generally, in place of the Euro- 

 pean ones which were for many years the main 

 reliance. The compilation will also serve a 

 useful purpose in showing the lines in which 

 additional digestion experiments are needed to 

 supplement the data already obtained, and in 

 calling attention to feeding stuffs which have 

 not been sufficiently studied as to their digesti- 

 bility. E. W. Allen. 



SOCIETIES AND ACADESIIES. 

 NEW YORK ACADEMY OF SCIENCES. 

 SECTION OF ASTRONOMY, PHYSICS AND CHEM- 

 ISTRY. 



A MEETING of the Section was held on Mon- 

 day evening May 7th. Mr. Bergen Davis read 

 a paper describing some new experiments in 

 stationary sound waves. The experiments were 

 in three groups, those with a sound wave ane- 

 mometer, those with the use of empty gelatine 

 medicine capsules instead of cork-dust to show 

 the Kundt figures, and those concerning the 

 longitudinal motion of a cylinder closed at one 

 end across the stream lines in a stationary sound 

 wave. 



The stationary sound wave was that pro- 

 duced in a stopped organ pipe, provided with a 

 glass panel for observation, when it was sound- 

 ing its first overtone. A thin rubber diaphragm 

 near the central node prevented air currents 

 due to the blowing of the pipe. The cups of 

 the miniature anemometer were made by di- 

 viding No. 2 gelatine capsules longitudinally so 

 as to form half cylinders and mounting them on 

 card-board arms. The anemometer rotated 

 with ten revolutions per second in the loop of 

 the wave and came nearly to rest in the node. 

 The rate of revolution at various positions along 

 the wave varied approximately according to a 

 sine curve. The maximum amplitude of the 

 wave as calculated from the above rate was 

 .57 cm. 



The Kundt's figure experiment was performed 

 by emptying a box of No. 5 gelatine capsules 

 into the middle of the loop. They arranged 

 themselves in rows across the pipe. Each cap- 

 sule attracted its neighbor at the ends and re- 

 pelled it at the sides. The experiment is quite 

 striking. 



The motion of a cylinder perpendicularly to 

 the stream lines was obtained by using a cap- 

 sule from which the cap had been removed. 

 Such a capsule moved in the direction of the 

 closed end with considerable force. This was 

 also shown by making a small mill with a cap- 

 sule at the end of each of four card-board arms. 

 The rates of revolution in various parts of the 

 wave made, when plotted, nearly a sine curve. 

 The force acting normally to the closed ends of 

 the cylinders was measured with a torsion bal- 

 ance. The square roots of the torsion deflec- 

 tions gave, when plotted, an approximate sine 

 curve. The experiment was performed in air, 

 illuminating gas, carbon dioxide and hydrogen. 

 The torsion deflections were directly propor- 

 tional to the densities of the gases. Professor 

 William Hallook first suggested the cause of 

 this eSect, showing that it was due to the prin- 

 ciple of Bernouilli, that a gas in motion is less 

 dense than the same gas at rest. The vibrating 

 air has considerable velocity while the air 

 within the cylinders is nearly at rest. The 

 force is due to the difference of density on the 

 two sides of the closed end of the cylinder. The 

 author used this principle to determine the am- 

 plitude of vibration. Professor R. S. Wood- 

 ward assisted him in applying the proper 

 hydrodynamical principles, and he calculated 

 that the change in density was such as to give 

 a pressure of 21 dynes per square centimeter, 

 while the amplitude was .33 centimeters. This 

 agrees closely with the value obtained with the 

 sound wave anemometer. 



Professor Hallock also exhibited some color 

 photographs and some sound wave photographs 

 taken by Professor R. W. Wood, of the Univer- 

 sity of Wisconsin. William S. Day, 



Secretary of Section. 



SECTION OF ANTHROPOLOGY AND PSYCHOLOGY. 



A REGULAR meeting of the Section was held 

 on May 28th. The first paper, by G. B. Ger- 



