132 



Prof. PoggendorfF on a new form of 



tations. I consequently think that its publication may be of 

 some service to physicists. 



The body of the instrument consists essentially of two parts, 

 namely : (1) A glass bottle A, with a rather wide neck and a 

 tubulus at the side. In my instrument this bottle is about 

 12 inches high and 6 inches in diameter. (2) An egg-shaped 

 glass vessel B, with a short neck above and a long one below, 

 which is ground so as to fit into the neck of the bottle A, and 

 reaches nearly to the bottom of it. 



An iron cap, provided with a passage which opens on the out- 

 side by the nozzle i, and 

 can be closed air-tight 

 by the cock f, is ce- 

 mented on to the tubu- 

 lus of the bottle A. 



In like manner the 

 upper neck of the egg- 

 shaped vessel B is pro- 

 vided with an iron cap, 

 the opening of which 

 can be closed by the 

 cock g. This opening 

 leads in the first in- 

 stance into the little 

 bottle d, which has the 

 iron nozzle k cemented 

 on to its neck. 



The last-mentioned 

 cock g has a threefold 

 purpose, and is corre- 

 spondingly bored. 



When its handle stands 

 vertically with the end|? 

 below, it establishes a 

 communication from the 

 vessel B to the small 

 bottle d, and, provided 

 the nozzle k is open, to 

 the air outside. 



If it is inclined at an 

 angle of 45°, it com- 

 pletely cuts off the vessel B ; and when placed horizontal with 

 the end p towards the left, it makes a communication between 

 this vessel and a lateral passage I, with which whatever is to be 

 exhausted is connected air-tight*. 



* In the figure this lateral passage is represented, for the sake of clear- 





'fV\ 



