REPORT ON CAPILLARY ATTRACTION. 293 



angle of inclination to any required magnitude, and was con- 

 venient for dipping the plates very frequently in the fluids. 

 The peculiar advantage of this method was, that the ascents 

 of different fluids could be observed under exactly the same 

 circumstances : for all the observations could be taken at 

 the same parts of the plates and with the same interval of 

 separation; and after experiments made with one fluid, the 

 plates could be conveniently cleared of all remaining moistux'e, 

 before experiments were made with another. When the same 

 capillary tube is used, it is difiicult to get rid of the moisture 

 adhering to the interior ; and when different tubes are used, 

 the experiments cannot well be under like circumstances by 

 reason of superficial inequalities in the glass surfaces, besides 

 that the exact proportion of the diameters is not readily ascer- 

 tained. The principal result that M. Link arrives at is, that all 

 the fluids rose to the same height. The fluids employed were, 

 distilled water, nitric acid, a solution of kali causti'jum (one oz. 

 to six of water), spirit of wine (very rectified), sulphuric asther, 

 and rectified sulphuric acid (sp. gr. 1*84). The ai.ther stood 

 lower at first, but after repeated dippings rose to the same height 

 as the water. The sulphuric acid was at first higher than the 

 water, but afterwards sunk to the same level as the rest. Pre- 

 vious experiments have uniformly assigned a less ascent to sether 

 and spirit of wine than to water, and a greater ascent to sidpliu- 

 ric acid. M. Link is of opinion, that the experiments were not 

 carried far enough, and that the different results of his own ex- 

 IJeriments are attributable to the repeated wetting of the plates 

 by dipping them in the fluids. In another set of experiments 

 the plates were of various substances ; viz. glass, copper, zinc, 

 copper and zinc plates soldered together, first, with the zinc 

 surface opposed to the copper, next, the zinc surfaces opposed 

 to each other, and then the copper surfaces opposed ; lastly, 

 wooden surfaces smeared over with tallow. The heights of as- 

 cent were very nearly the same for all these, excepting that the 

 tallow plates did not give quite so high a column. It would 

 seem, then, that the heights of ascent under similar circumstances 

 are alike independent of the fluids and solids. It is remarkable 

 that this result miglit have been looked for from either Laplace's 

 or Poisson's theory: for by either theory the height of ascent 

 in a given capillary tube, or between parallel plates separated by 



a given small interval, varies as — , when the fluid completely 



wets the solid*; and as H, in this case, depends only on the 



• See p. 2G3. 



