Ivi 



showin<i^ that the spot has resumed its drift in the direction of 

 the rotation, or has at least slackened its drift in the opposite 

 direction. 



The spot will be observed during the present opposition when 

 a full discussion of the observations of both years will be pre- 

 sented. 



Mr. Seddon gave as his conclusion for a resistance formula 

 for river flow — 



/? = ^Ftan if dL. 

 where 



R rr the energy in foot-pounds per second expended 



in flow through the distance, dL. 

 A =: the water area of the cross-section. 

 V z= the mean velocity in feet per second, 

 and f =: a. mean angle of instantaneous divergence of par- 



ticles from the direction of the mean stream lines, 

 or Ktan <p =z a mean velocity of circulation at the section. 



Prof. Wheeler exhibited a live cray-fish which he had found 

 on Nov. 36, 1 89 1, at a depth of 5 feet in very solid dry clay on 

 West Pine st., near Forest Park (St. Louis), on the site of an old 

 swamp. It was dormant when first unearthed, and a continuous 

 hole extended from it to the surface. 



December 21st, 1891. 



President Nipher in the chair ; fifteen members present. 



Prof. Nipher read a note on the Rotary Polarization of Light 

 in Hydro-carbon Serial compounds. 



The object of the paper was to show a method of determining 

 the relative dimensions of the molecules of such Serial com- 

 pounds. 



EDMUND A. ENGLER, 



Recording Secretary. 



