CAPILLARY TtJBES. . f 49 



Abstract of a Memoir on the Theory of Capillary Tubes. B/ 

 M. La PL-ACE.* 



A HIS memoir, destined to appear among those of the first 



class of the Institute, is preceded by the following analysis of the 



theory it contains. 



Clairaut was the first who submitted the phenomena of capil- The theory of 



1 • ■ 1 • rU •./ 7 c,ipi:lary tubes 



lary tubes to strict and accurate analysis, in his Irattc sur la ^^ t'lairaut 



Figure de la Terre, But his theory, though exposed with the 

 elegance which characterizes that excellent and important work, 

 leaves to be desired a compleat explication of the chief of these 

 phenomena; namely, why the elevation of the fluid above its 

 level in' tubes of the same matter^ is inversely as their diame- 

 ters. This great geometer is contented to observe, without —imperfect, 

 proving it, that there must be an infinity of laws of attraction 

 which, when substituted in his formulas, give that result. I have 

 loYig sought to supply what is waiiting in the theory of Clai- 

 raut. New researches have at length conducted me not only 

 to ascertain the existence of such laws, but have likewise shewn 

 that every law, according to which the attraction ceases to be 

 perceptfliie at any perceptible distance, must give an elevation 

 of the fluid in the i".verse ratio of the diameter of the tube ; and 

 the result is a complete theory of this description of phenomena. 



Clairaut supposes that the action of the'capillary tube is sen- Clnirant sup- 

 sible upon the infinitely thin column of the fluid which passes fa'i'v ntt'-ac'loni" 

 through the axis of the tube. I differ fror.i him in opinion in this evtended to the 

 respect, and think with Hawksbee, and many other philosophers, ^.^i^g ?' 

 that the capillary attraction, hke the refractive force and all 

 the chemical affinities, is not sensible, except at imperceptible 

 distances. Hawksbee has observed, that in glass tubes, whether But this is not 

 they be very thin or very thick, water rises to the same height the facts!' "^' 

 whenever the interior diameters are the same. The cyHndfi- 

 cal zones of the glass v/hich are at a sensible distance from the 

 interior surface, do not therefore contribute to the ascent of the 

 water, though meach of them separately taken, this fluid would 

 rise above its level. A viry simple experiment also proves the 



* Read to the French National Tagtitute, 23d Dec. 1805, and 

 translated from the paper comraimieated by this author to the 

 Journal de Physique, Ixii. 120. 



Vol. Xiy.— July, 1806". Kk truth 



