On Capillary AB'ion. I95 



of Its folidlty, and fcarce an attempt is made to eftablifh an- 

 other theory. The celebrated Clairaut, indeeti, has cal'ually 

 touched on the lubjecl of capillary aftion in his Treatife on 

 the Figure of the Earth ; but his invettigalion of that phae- 

 nomenon is loft in a chaos of calculation. M. Lalande, who 

 is fo aclive a writer, has tried to unravel it: the aftronomer 

 does not appear, however, to have fucceeded. I content my- 

 felf with this general notice of his little tra6l ; for to refute it 

 is much eafier than to render it diftin£lly intelligible. 



But, when we coolly confider Jurin's account of capillary 

 a^lion, we are furprifed that it could obtain fuch fuccefs. It 

 is in appearance fimple indeed, and plaufible ; but it will not 

 bear the flighteft examination. The water is conceived to be 

 kept fufpended in the tube by the attraftion of the fmall ring 

 of glafs immediately above the interior furface. But I aik. 

 Ought not the ring helotu to exert an equal force in a con- 

 trary direclion, and confequently deftroy the effctl of the 

 former? This argument it feems impoflible to elude, and to 

 expand it would be fuperfluous. We muft therefore regard 

 the common account of capillary aftion as entirely without 

 foundation. 



It may well furnifh matter for furprife and mortification to 

 remark fuch a glaririg overfight committed in the very porch 

 of the phv'fical fciences. But if we extend our obfervalions 

 we fliall foon be convinced that the popular branches of phi- 

 lofophy, with all their fuppofed improvement, are in general 

 ftill very defective and erroneous. Thofe flowery departments 

 have been left to the culture of a fecondary order of men, 

 whofe imagination was commonly more powerful than their 

 judgment. In every age the vigour of genius has been di- 

 rected to the fubllmcr parts, and thofe united efforts have 

 reared a flupendous monument of I he penetration and re- 

 fources of the human mind. 



In attempting to explain the mode of capillary a6lion, the 

 chief difficulty leems to arife from the prejudice that a ctr- 

 ttcai attra6lion is necefTary to account for the elevation of 

 liquor in the tube: vet this is afl'uredly not the primary di- 

 re6ti(jn of the force; for, the aClion of glafs being evitlently 

 confined within very narrow limiLs, that virtue muft be dif- 

 fufcd over the int(Tnal furface of the tube, and confequently 

 mud exert itfelf laterally ^ax at right angles to the fides. Nor 

 is it difticult to conceive how a lateral adion may caufc an 

 afecnt. \Vc know that in fluids a force imijreffed in one di- 

 rtdf ion is capable of propagating itlclf in all directions. The 

 tenduncy of the hquur to approach the glals, mull uccafion it 

 N -J, to 



