1^4 On Capillary A&ion. 



and efTential law of nature. Gravitation itfelf Is only a branch 

 of tliat law, from which are derived the various conCtitution 

 and all tlie divcrfiticd properties, of bodies. The mutual atSlioa 

 exerted bciween two elementary portions of matter is, in the 

 lans'uage of modern algebraifts, always fome fuvMion of their 

 diftance. At proximate diilanccs, this funftion mull change 

 repeatedly, and with different degiees of intenfity, from po(i- 

 tive to negative, or from attraiStion to repulfion. Hence the 

 varied ftruAure and compofition of bodies. It is indifferent 

 whether we confider the elementary portions of matter as 

 points, atoms, particles, or molecules. Their magnitude, if 

 they have any, never enters into the eftimate. WJien the 

 ditlance is conliderablc, the law of aftion becomes confounded 

 with that of gravitation, and is of fuch remarkable fimplicity 

 as to qualify it for the hapy-ieil application ever made of the 

 mathematical fcienccs. Could we afcertain the gradations 

 at near ditlances, we might determine the (Irufture, affini- 

 ties, and mutual operations of bodies, with the fame cer- 

 tainty as we compute the revolutions of the planets. But 

 fuch a difcovery feems placed beyond the reach of the human 

 faculties. However, by a fcrnpulous attention, we may dif- 

 cern certain inllances of the approximation and tranfition of 

 corpufc-ular forces. And I hold thofe fa6ls to be the more 

 valuable, as they form the intermediate link between the me- 

 chanical and the chemical phoenomena. 



Of this kind I conlider the afcenjion of icater and other 

 liquids in capillary tubes. This faA is fo familiar that I need 

 not flop t9 defcribe it. It was firft noticed by the Academy 

 del Cimento, at Florence,, early in the 17th century; but 

 feems not to have been much regarded in the fequel. After 

 the promulgation, however, of the Newtonian fyflcm, the 

 fiibjeft was revived with ardour. It was juftly confidered as 

 affording intuitive evidence of the reality of attvaftion. About 

 the begimiing of the i(Sth century, Hawkfbee, in f'ngland, 

 made fome excellent experiments on capillary action ; and 

 Miinchenbroeck purfued the farlie courfe in Holland. Similar 

 experiments were performed in France; but in that country 

 the Cartefian philofophv was then in the height of its career, 

 and no deliberate attention could be paid to fails which ap-- 

 peared to countenance an oppofite fyllem. About the fame 

 period Dr. .Turin publiflied, at London, an elaborate differta- 

 tion on the cauf,; of capillary a6lion ; and his explication of 

 that curious iA.(.-\. feems, either from conviftion or fupine 

 acquieCcence, to be almoft univerfally adopted. It is repeated 

 in all the elementary books of natural philofophy. It con- 

 tinues to muinlain the fame credit : no fuluicioa is ever ftarled 



of 



