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UNIVERSITY OF COLORADO STUDIES 



little over one mile, and the barometric pressure, therefore, only 

 about sixty-one centimetres, this means that the siphon worked nine 

 centimetres above the barometric height. 



The most plausible explanation of the above fact is that the at- 

 mospheric pressure is not the only force pushing the mercury up the 

 shorter leg. It is drawn up partly by the cohesive attraction of 

 parts of the mercury for each other, and the column is kept from 

 dwindling by the adliesive force exerted by the sides of the tube on 

 the mercury. 



It follows from the above that if a mercury siphon is placed 

 under the receiver of an air pump, it can be made to work over a 

 height of several centimetres, even though the air pressure is reduced 

 to only a few millimetres. This experiment also has been shown to 

 the writer's students. The apparatus was similar to that described 

 above, except that the tubes were much shorter. 



