laiy. 



254 CAPILLARY TUBES. 



Laplace's theo- two Intensities be equal, the surface of the fluid in the tube will 

 tC^and de!^^ ^^^ concave and hemispherical, and' the fluid will rise above the 

 pressiou of level. If the intensity of the attraction of the tube be nothings 

 effect of aVtrac- "^ insensible, the surface of the fluid in the tube will be convex, 

 tion which is and Kenjjspherical, and the fluid will be depressed below the 

 called capil. j^^.g]^ Between these two hmits, the surface of the fluid will 

 be that of a shpcrical segment, and it will be concave or con-, 

 vex accordingly as the intensity of the attraction of the matter', 

 of the tube upon the fluid shall be greater or less than the half 

 of that of the attraction of the fluid upon itsejf. 



If the intensity of the attraction of the tube upon the fluid 

 surpass that of the attraction of the fluid upon itcelf, it nppear« 

 probable to me that the fluid in that case, attaching itself to 

 the tube, v/iil form an interior tube, which alone will raise the 

 fluid, of which the surface will be concave and hemispherical. 

 I presume that this is the case with water in a tube of glass. 



After having considered fluids terminated by spherical sur- 

 faces, I consider them as terminated by cylindrical surfaces. 

 This case is that of a fluid included betwecji two planes very 

 near each other, and having their lower extremities plunged in a 

 vessel containing the same fluid. I find by analysis that the 

 fluid ought to rise or be depressed accordingly as the cylindric 

 surface of the fluid is concave or convex, and that this eleva- 

 tion or depression also follows the inverse ratio of the distance 

 between the planes, I find also that the elevation or depression 

 is equal to that which would take place in a cylindrical tube of 

 which the internal scnii-diameter should be equal to, that dis- 

 tance. Having obtained this result by analysis, I proposed to 

 M. liauy to verify the same by experiments, and he found it 

 perfectly conformable to those which at my request he made. 

 And afterwards, upon revising what has been written on the 

 capillary action, I saw that these experiments had already been 

 made with great cajre in the presence of Jhe Royal Society of 

 London, under the eyes of Newton, and that their result is 

 exactly conformable to that of the analysis. This may be seen 

 by the following passage in his Optics, an admirable work, in 

 which that profound genius has anticipated beyond the times in 

 which he lived, a great numberof original views which have been 

 confirmed by modern chemistry. '* And of the same kind *' (says 

 he, question 31.) " with these experiments are those which 



*' follow 



