lExtrdSl of a Memoir ofi lElaJl'iclly. t^^ 



' The cohipreffion and re-eftablifhment of caloric may ferve to 

 explain alfo the ofcillations of the moleculEe of a tube of glafs 

 terniiuated by a ball of the fame nature, when rubbed with 

 a moiftened fponge in order to obtain from it acute tones. 

 The molecula; of the tube having, by the extension which it 

 experiences, quitted the pofition proper for their equilibrium, 

 tend to return to it ; and as by the velocity acquired they go 

 beyond t!ie term from which they fet out, the interpofed ca- 

 loric is comprefled, it re-cflabliihts itfelf with a force equal 

 to the compreflion, and repels the two parts of the tube to 

 the diftance at which they were at firft, which occafions an 

 ofcillatory motion until it has been deftroyed by the refift- 

 ance of the air. 



We might, ftriftlv fpeaking, explain, without the inter- 

 vention of caloric, the elafticity of the llring of a violin, or 

 of a bell, put into vibration : but from what hcis been faid, 

 It feems to aft the moil confpicuous part. 



Elafticity manifefts itfelf with lefs energy in liquids than 

 in folids, and yet the former contain more caloric. The 

 rcafon is plain ; it is becaufe their moleculn?, being exceed- 

 ingly moveable, they can eafily vvlihdraw themfelves from 

 the compreffing forces ; but they are elaftic, fuice they ha\'e 

 the property of tranfmitting founds, and of recoiling back on 

 themfelves. 



It muft have been remarked, that the accumulation of ca- 

 loric diminifhes the fpring of fulid or fluid bodies : in gafeous- 

 bodies, on the other hand, this elafticity is increafed by the 

 accumulation, becaufe thefe bodies, being held in folution 

 in the caloric, participate in its mechanical properties, and 

 chiefly its elafticity. 



To increafe or produce eladicity in certain bodies, we 

 jnu(t employ means proper for bringing together their mo- 

 lecular and keeping the caloric in a ftate of great oompref- 

 fion. The harder, therefore, that a body is, provided it ij 

 hot fo in the extreme degree, the more it will be elaftic. It 

 becomes, indeed, lefs flexible; but this inconvenience may 

 be remedied by rendering the body thin, fmce its molecul:e 

 will then be lefs difplaced during flexi«n. There are two 

 things, then, to be confidered in elafticity ; the rapidity of 



the 



