

uu 



. 



DIFFEEENT LIQUIDS IN COMMUNICATING VESSELS. 185 



column of paraffin-oil above the surface of contact 

 ust therefore be 50 cm , in order to balance a column 

 of water which has only a height of 40 cm , and the 

 case would be precisely the same if the communi- 

 cating vessels had different forms, for instance those 

 of B or C in fig. 132; for the pressure upon the 

 surface a b depends not on the form of the vessels, but 

 solely upon the vertical heights a c and b d. It 

 will be seen that the height of the column of water 

 (40 cra ) is contained in the height of the oil (50 cm ) 

 precisely as many times as the specific gravity of the 

 paraffin-oil (0*8) is contained in the specific gravity 

 of water ( 1 ). The perpendicular heights measured from 

 the common surface of contact of two liquid columns in 

 communicating tubes are inversely proportional to the 

 specific gravities of the liquids ; thus 40 : 50 : : 0*8 : 1. 



If both liquids have the same specific 

 gravity, that is, if their specific gravities 

 are in the ratio of 1:1, the heights 

 will clearly be also as 1:1. The case 

 of two different liquids having the same 

 specific gravity is rare, but the result 

 with reference to the heights will ob- 

 viously be the same if, instead of two 

 different liquids of equal specific gravity, 

 there is one and the same liquid in both tubes. Hence 

 it follows that for the same liquid: In communicating 

 tubes a liquid rises to the same height. This is shown in 

 fig. 133. 



In the preceding experiments the height of the liquid has been sup- 

 posed to be independent of the internal width of the vessels ; but this 

 is not the case if the internal diameter of a vessel is less than l cm . 

 In such vessels the height of a liquid is influenced by forces which 



FIG. 133. 



