510 



SCIENCE. 



[N. S. Vol. IX. No. 223. 



tire protein contents of cells, especially upon 

 cliloroplasts. 



A complete account of the work with il- 

 lustrations will be published soon. 



Albert F. Woods. 

 Division of Vegetable Physiology 

 AND Pathology, U. S. Dept. Ageicultuee. 



AN AUTOMATIC MERCUEY PUMP. 

 Although there is nothing especially 

 new in regard to the pump proper, the 

 method of electrical control may be suffi- 

 ciently novel to warrant a brief description. 



flask filled with mercury. A tight joint is 

 made between the flask and pump by a rub- 

 ber stopper. This stopper also serves as a 

 flexible support for the body of the pump. 

 The exhaust tube is sealed into the pump 

 just above the point at which the pump 

 passes into the flask. The arrangement is 

 best shown by the figure. 



The tube to be exhausted is attached to 

 the pump, through a drying bulb filled with 

 anhydrous phosphoric acid, by a simple 

 ground joint with a mercury seal. The 

 valve at the top of the pump is ground to 



fHi^T 



The pump proper is a modification of a 

 common form of Geissler pump. It con- 

 sists of a long glass tube, about 1;^ inches 

 in diameter, which has a mercury trap and 

 a small glass valve at the top. The bottom 

 of the tube is drawn down and dips into a 



fit its seat and so weighted by filling with 

 mercury that it closes, leaving sufficient 

 mercury above it to form a tight joint. Di- 

 mensions which give very satisfactorj^ re- 

 sults are shown on the figure, Suction is 

 applied permanently to the top of the pump 



