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XXX. On Capillary Aflion. JByJoHN Leslie^ Efq* 



A HE principle of univerfal attraftion, having finally fub- 

 dued every fpecies of oppofition, is now fixed on a bale never 

 to be fliaken. Many are the fruitlefs attempts to explain its 

 operation by the impuUlve energy of fome invifible impalpa- 

 ble fluid : but thefeowe their birth to metaphyfical prejudice, 

 and are jufily difcarded by all fober and refleding inquirers. 

 Nor is the fuppofition of fuch mechanical intermedia merely 

 repugnant to the fpirit of true philofophy ; it is direftly con- 

 tradi6led by recent difcovcries. When an impulfe is com- 

 municated to any mafs or fyftem of particles, it is transferred 

 along the chain by a feries'of pulfations, each particle in fuc- 

 ceflion feeling the adlion and fuffering a momentary derange- 

 ment. Motion is therefore propagated in the fame manner 

 as found, and the celerity of its tranfmiffion muft depend on 

 the mutual diftance of the affected particles and the relative 

 force with which they are conneiiled together. In moft cafes, 

 indeed, that come under obfervation, it is impoffible to di- 

 flinguifli the interval between the origin and the '.erminatioii 

 of an impulfe, which is thence very generally imaging to a6t 

 fimultaneoufly through the whole line of its communication. 

 But, though the rapidity of tranfit outftiips the quicknefs of 

 our fenfations, it llil! requires a certain lapfe of time. Nay, 

 on the jull ellimate of this principle, — on the duration of ef- 

 fe£t, — (refined as it may appear,) depends the theory of the 

 tools and iDanipulations ufed in moll of the mechanic arts. 

 Nor is the exiitence of fuch a fmall yet finite moment a 

 mere abftractionj it is the neceflary refult of the known pro- 

 perties of matter. Were we to fuppofe that the fun a6ls on 

 the planets by the intervention of fome fubtle medium dif- 

 fufed through the celeftial fpaces and endowed with the moft 

 powerful elafticity, a very confiderable meafurc of time would 

 be required to propagate the imprelfion. If we afcribed to 

 that fluid, for example, the relative denfity and elafticity of 

 hydrogenous gas, alnioft five years would be fpent in convey- 

 ing the impulfivc energy to the earth. But it is proved, by 

 fome late and very nice refearches of IVl. Laplace on the ir- 

 regular! lies of the planetary motions, that the attra6livc force 

 of the iuu is exerted fimultaneoufly at all diltances. The 

 notion of an intermediate fluid is thus entirely precluded. 

 The principle of ailion at a dijlance is therefore a primary 



• Communicated by 'he Author, 



VoirxTvrNir55: N and 



Dettmbtr i8o2. 



