^4 FOURTH REPORT 1834. 



molecular action of the parts of the fluid on each other*, the 

 simplest supposition respecting it is, that it varies as p ; whence 

 it would follow that the height of ascent is the same for different 

 fluids. 



In the applications of the theories of Laplace and Poisson to 

 Gay-Lussac's experiments on the ascents of fluids in capillary 

 tuhes, and the weights of the fluid columns raised by circular 



2 

 discs, the values of the constant — for the different fluids, were 



a 



borrowed from the first class of experiments, and being em- 

 ployed in the theoretical formulae, gave results according M'ith 

 the other class. If those values were incorrectly determined by 

 the experiments, this accordance can only be explained by sup- 

 posing the cause of error to be of the same kind and to act in 

 the same degree in the two classes of experiments. 



M. Link remarks that there is an essential difference between 

 the ascent of fluids against solid surfaces not previously wetted, 

 and the remaining height of suspension after the wetting. Tal- 

 low, for instance, %rill scarcely allow water to ascend at all in the 

 first instance ; but after being moistened, will sustain a suspended 

 column, of nearly the same height, according to the experiment 

 mentioned above, as when other substances are employed. The 

 theory of the^tsf ascents, must be of a very complicated nature, 

 on account of the difficulty of estimating the amount of various 

 retarding causes, such as greasiness, and the inequalities of the 

 solid surfaces. But the theory of the remaining suspensions 

 that result fi-om wetting the surfaces, is of a more simple nature. 

 M. Link adduces an explanation of this fact, founded on a theory 

 of fluidity developed in the first part of his paper, in which, set- 

 ting out with Newton's definition of a fluid, he is led to regard 

 it as composed of solid particles in an extreme state of pulveriza- 

 tion, and aggregated like the grains of a heap of sand. What- 

 ever in other respects may be the comparative merits of this 

 view of the nature of fluiditj', and that adopted by Young and 

 Poisson, the latter has the advantage of being more readily made 

 a basis of calculation. 



» pp. 275 and 285. 



