202 



MOTIONS OP PLCIDS. 



Uratum, with a glafs rod, the watej illes in an inftant with 

 vivafcity, leaving the bottom oi the velFel uncovered; when 

 it has reached the maximum of dilperfion it returns, and 

 covers again the bottom of the veflel which it had quitted. 

 Ditkof difper- 2. I call that part of the veflel which is abandoned by the 

 water the di/Jc of difperjion. In the preceding experiment, 

 this difk (hows a perfetl drynefs and all its natural polifli. 

 The repitltionof 3. Th** repulfion becomes lefs confidcrable, and the difk of 

 kffeiis its dilperfion fmaller, in proportion as the experiment is repeated 



cft'efts. in the fame water. This arifes from the water becoming gra- 



dually faturated with alcohol. 

 Influence of the 4. The nature of the vefTels has no influence on thepreced- 

 ^'^ ^** ing experiment, nor on thofe which follow. They take place 



equally in veflels of porcelain, earthern ware, glafs or 

 metal. 



5. The form of the veflels has much influence on the 

 fecond period of the phenomenon, that is to fay, on the 

 return of the water, and on the difappearance of the di(k 

 of difpeifion. 



If the veflTel is a little concave, the water always comes 

 back, and covers the bottom of the vefl^el again. It will be 

 obvious, that this is the neceflary efted of its gravity. 



If the velfel is flat, the water only returns when the difk of 

 difperfion has not attained too great a diameter. 



If the bottom of the veflel is a little convex, the water 



does not return af'.er having been difperfed, and it mufl be 



evident, that to do fo it would a6t contrary to the operation 



of its own gravity. 



Motion of the ^« I^eing defirous to render the obfervation of the motions 



e^tpcikd fluid 3 of the expelled fluid eafier and more perfed, I fubftituted 



tindure of turnfole, which, as is known, is only water 



coloured by turnfole, for pure water. The refults were the 



fame, but much more ienfible; and I could then readily 



difiinguifli aii undulating or trembling motion on the internal 



edge of the water which furrounds the difk of difperfion ; a 



molion which proves the continual emilTion of the alcoholic 



particles againfl this interior edge, and determines the removal 



of the water. 



«ndof theim- 7. But to complete the proof of the explanation which I 



celling ui . \^^yje juft given of the phenomenon, it was alfo neceflTary to 



render the motions of the impelling fluid fenfible ; I fucceeded 



by 



