RECORDS 503 



The following candidates for resident membership, approved 

 by the Council, were duly elected : Prof Charles Lane Poor, 

 4 East 48th street; Riccardo Bertelli, 409-415 Forsyth street. 



Richard E. Dodge, 

 Recording Secretary. 



SECTION OF ASTRONOMY, PHYSICS AND 

 CHEMISTRY. 



November 5, 1900. 



Section met at 8:30 P. M., Prof Wm. Hallock presiding. 



The minutes of the last meeting of Section were read and ap- 

 proved. 



The following program was offered : 



F. L. Tufts, Flow of Air at Different Pressures Through 

 Granular Materials. 



Summary of Paper. 



The experiments described by Mr. TuftS were made in con- 

 nection with others on the transmission of sound through the 

 same materials. Three different materials were experimented 

 on, composed of lead shot of three sizes, the diameters of the 

 shot being respectively 4.37 mm., 2.79 mm., and 1.22 mm. The 

 shot was placed in a tube and air was forced through at different 

 pressures, the rate of flow of air being measured by a gas meter, 

 and the pressure differences by a water manometer. It was 

 found that for a given size of shot and a given pressure gradient, 

 the rate of flow was independent of the length of the column of 

 shot through which the air flowed. The rate of flow, however, in 

 the three cases experimented with did not increase as rapidly as 

 the pressure gradient. This was more noticeable with the coarse 

 shot than with the finer. For pressure gradients of about 0.0 1 

 cm. water pressure per centimeter of length of material, the rate 

 of flow through the coarsest shot was ten times the rate through 

 the finest, while for a pressure gradient fifty times as great, the 

 rate of flow was a little less than three times as great in the 



