Capillary Attraction. 345 



and 



from which if we subtract one sixth of the diameter, or 0,3173, 

 we have 15,5783 for the altitude h of the lowest point of the con- 

 cavity of the meniscus, which differs only 0,0078 or 0,0003 of 

 of an inch from 15,5861, the observed altitude. 



If we apply the same formula to M. Gay Lussac's experiments 

 on alcohol, we shall find for the constant quantity 



2 *PP' = 6,0825, 



as deduced from the first experiment, and h = 6,0725, which 

 differs only 0,01147 or 0,00045 of an inch from 6,08397, the ob- 

 served altitude. 



From these examples, it will be seen that the mean altitudes, 

 or the values of h', are reciprocally proportional to the diame- 

 ters of the tubes very nearly ; and that in accurate experiments, 

 the correction made by the addition of the sixth part of the 

 diameter of the tube is indispensably requisite. 



459. If the section of the bore in which the fluid ascends is a Fig.224. 

 rectangle, whose greater side is a, and smaller side tf, the base 

 of the elevated column will be a <?, and its perimeter 2 a -j- 2 9. 



Then the meniscus will be equal to the small rectangular prism, 

 whose base is a $ and height \ <T, minus the semicylinder whose 

 radius is \ d and length a ; accordingly, we have for the solidity 

 of the meniscus, 



ad 2 and 2 _ ad 2 

 that is, 



Hence, if in the general (i.) equation we substitute for c its equal 

 Mech. 44 



