140 



J. A. POLLOCK. 



A SIMPLE FORM OF SPRENGBL VACUUM PUMP. 



By J. A. Pollock. 



Professor of Physics iu the University of Sydney. 



[Read before ike Royal Society of N. 8. Wales, October 2, 1907.'] 



A simple Sprengel vacuum pump which I have designed, 

 has been used in the Physical Laboratory of the University 

 of Sydney for some years and has proved convenient ; a 

 description is now given, as possibly the form may be found 

 useful by other experimenters. 



The apparatus is a modified short fall Sprengel. The 

 feature of the pump, which is believed to be new, is that 

 the raising of the mercury, necessary for continuous work- 

 ing, is effected by evaporating the mercury at a lower and 

 condensing it at a higher level. This principle may be 

 equally well applied to other forms of vacuum pumps. 



