More than a year after the publication of Dr Young's paper, Al. La Place published a supplement to the Me canique Celeste, upon capillary attraction, where he has proposed a theory, which has led him to several conclu sions that Dr Young had already obtained by a more shn ple route. It is a very singular circumstance, that La Place should take no notice whatever of Dr Young's la bours, as the volume of the Transactions which contained them, and several periodical works in which they were noticed, must naturally have found their way to Paris. La Place supposes, from Esp. 11. and 18. that capillary action, like the refractive force, and the chemical affini ties, is only sensible at imperceptible distances ; that a narrow ring of glass, immediately above the surface of the fluid, exerts its force on the water ; and that this force, combined with the weight of the water, and the cohesion of its particles, produces the concave surface or meniscus of fluid with which the column is always terminated. Ile supposes this meniscus to he sustained by the action of the glass, while it exerts its own attrac tion on the fluid particles immediately below it, by means of which their gravity is diminished, and the water con sequently rises in the tube; and he has determined the form or the meniscus to be that of a hemisphere, and its attraction to be equal to that ofa spherole of water of the same diameter. Hence the attraction of the menisrus Will be inversely as its diameter, or the diameter or the tube, that is, as the weight of the elevated column, and therefore the heights of ascent must be inversely as the diameter of the tube. " Since it has hitherto been usual with natural philosophers," says La Place, tr to consider the concavity and convexity of the surfaces of fluids in capillary spaces, as a secondary of capillary attrac tion only, and not as the principal cause of phenomena of this kind, they have not attached much importance to the determination of the curvature of these surfaces. But the theory which has been here advanced, having she WII that all these phenomena depend principally on the cur vature, it becomes of consequence to examine it." In opposition to the high authority of La Place, we agree with Professor Play lair in thinking, " that the principal and primary cause is that attraction, which sustains the meniscus, and enables it to act on the water below with out being drawn out of its place. It is not the concavity of its'§urface that makes the water in the tube press less in the bottom than if its surface were plain; but it is the attraction of the glass that produces, in a manner equally direct, both the concavity and the diminution of pres sure." The fact mentioned in Exp. 12, has been as
cribed by La Place to the action of the drop upon the column, in consequence of its convexity ; while Air Playfair supposes the additional elevation to be occasion ed by the action of the bottom and outside of the tube upon the drop, by which the column or water is lifted up to a higher level. We are disposed, however, to think, that the column of water, after being raised above its ordinary height in the tube, as in Esp. 12, is pre vented from obeying the force of gravity by the force with which the drop below adheres to tile bottom of the tube, and the force by which it resists any coange of form ; for the descent of the column to its usual height could only take place, either by detaching the drop al together from the tube, or by giving it a more spherical, or a more elongated form. If the other explanations were true, then the column might be raised above its usual height in the tube, by placing a drop of water on the outside, and allowing it to descend to the luttom of the tube, where it would exert its force, according to La Place, or be acted upon by the tube, according to Mr Mayfair, which is not the case. For norther info• mation on this subject. see I looke's Micographza. Jurin, Phil. Trans. No. 335, and No. 363. 11 tini:t0E's Lec tures, ii. p. 47. Ilauksbee, Phil. Trans. 1706, p. 223; 1709, p. 258; 1711,p. 393; 1712, p. 413; 1712, p. 539; 1713, p. 151. Taylor, Phil Trans. 1712, p. 538; 1721, p. 209. Bull finger. Conn. Prtrop, ii. 233; iii. 281. NI us chenbrot k de trails i'Ureis, Diss. Phys. 271. Weitbrecht, Com. Petrol?. viii. 261; ix. 275. Gellert, Id. xii. 293. 302. Scgner, Caro. Golfing-, 1751, i. p. 301 ; La Lande sur la cause de l'clevation des liqueurs, 12 Paris, 1771. MJrveau Rozier, Journ. i. 172, 460. Dutour, Bozic!. Journ. xi. 127 ; xiii. Sup. 357; xiv. 216; xv. 46, 234; XV;. 85; xix. 137, 287. Milan JOUT11. liv. 126; arm Rep( mory of .,irts, xvi. 427. Von Arnim in Gil bert's Journal, iv. 376. Hallstrom, Id. Nil•. 423. Clai rant rip de In Figure de la Time !frees des de I' Hydr,statique. p . I. Dr T. Your a:: 0,1 The Cohesion of Fluids, Phil. n'tins. 1805, anti in his :Vat. Phil. ti. p. C19. La Place's Mccanique Celeste. Sup. au Dizieme Liv. Play lair's !frailties of ./at. %()]. i. p. 181. See also Ain Esiox and !Iv() ItO bVNAMIr s. CAPITANATA. See NerLes.