36 On the Motions of Camphor and Odorant Sodia, 



water with the camphor, produced by a fubtile oil proceeding from the camphor itfelf ; but 

 that it is owing merely to the cohefion between fat or oily bodies and water. Oils poflefs 

 much adhefion or attradlion of furface * with water ; but they have no cohefion or affinity 

 of aggregation, nor of compofition with that liquid. The water which furrounds oily or 

 fat bodies, fuch as a piece of camphor, having no degree of cohefion with that fubftancc, 

 appears to retreat from it ; that is, by^ abandoning itfelf intirely on its own force of aggre- 

 gation it is drawn off on all fides, which caufes a yacuity round the camphor. If it were 

 an elaftic odour, or an oily fluid proceeding from the camphor, which produces this pheno- 

 menon, the fame efFedt would not take place in bodies which have no fmell. But the phe- 

 nomenon is the fame, when inftead of camphor, fmall pieces of white wax or hardened 

 fuet are employed, which are fubllances as every one knows, which have fcarcely any 

 fmell, containing an oil which is not volatile, and requiring a confiderable degree of heat 

 to become fufed. 



Hence it appears, the experiments of Prevofl: do not prove that odoriferous bodies are 

 furroundedwith an atmofphere pofleffing a degree of elafticity or power capable of impel- 

 Jing the water which furrounds them ; and that it has been falfely imagined that by this 

 means the emanations from odoriferous bodies might be rendered perceptible. 



I did not obferve, what Prevoft fays he remarked, that fragments of camphor about the 

 fize of a pea,' placed on a round piece of gold or filver foil floating upon water gave it 

 motion. The camphor itfelf is not fufceptible of any fpontaneous motion, nor can it 

 impart it to light bodies which are on the water, unlefs it immediately touches that liquid. 

 It is the fame with regard to the oils, whether volatile or fixed ; they cannot impart the 

 leaft degree of motion to the lighteft body that floats upon water unlefs they touch it. I 

 have made feveral trials, by putting drops of ethereal or volatile oils on fmall pieces of 

 gold or Giver leaf that floated upon water. Tiie flighteft impreflion would have caufed 

 them to move, yet I never obferved the leaft motion in any of them. Venturi alfo had 

 the fame refult in an experiment with burning or heated camphor, placed on a piece of 

 cork which floated upon water. When the camphor came in conta£t with the fluid, it 

 imparted a rapid motion to its fupport, which, on the contrary, became motionlefs when 

 the water was not touched by the camphor. Hence he concluded, that the motion in 

 queftion does not depend on the proje£lion of volatile particles proceeding from the cam- 

 phor, but that it is the water alone which excites it by its aftion. 



Prevoft and Venturi remark, that if the furface of the water be touched with oil of 

 olives, or any other volatile oil or odoriferous fluid, when the camphor begins to move, 

 the motions immediately ceafe. This only tends to confiirm the explanation I have given 

 of the motion of the camphor and oleaginous bodies on the furface of water. The cam- 

 phor derives its motion only from the expanfion of an oil, which is attracted by the furface 



* See my explanation in Am, di Ctim, Italian!, torn. V. 



of 



