Ou the Motions of Camphor and Odorant Bodiet. 37 



of the water *. The reafon therefore why a drop of oil, whether fixed or volatile, ftops 

 the motion of the camphor, is, that thefe oils are more ftrongly attrafted by the furface of 

 the water, than by that of the camphor ; hence they adhere to that fnrface, and by co- 

 vering it prevent the efFedl: of its attradtion for the oil of the camphor, and confequently 

 prevent the expanfion of that fluid f. This property of preventing the motion of the 

 camphor is not peculiar to the oils ; all the cereal and leguminous farin2e, &c. the juices 

 of the tithymate, and other lafleous plants, which, as I have obferved in the memoir 

 before-mentioned, have a great affinity for the furface of the water, are invefted with 

 fimilar properties. 



Cit. Venturi has nearly difcovered the real explanation of the phenomenon. Having 

 obferved that a fmall quantity of oil (lopped the motion- of camphor in a bafon of water, 

 he concluded that this oil, which extends over the water like an imperceptible film, is the 

 caufe of the fufpenfion of motion in the camphor, becaufe, by occupying the furface of the 

 water, it prevents the camphor from expanding. Whence he feems to be of opinion, 

 that the motion of pieces of camphor upon water proceed from the expanfion of an oily 

 fubftance from the camphor upon the water itfelf. This is the explanation which I have 

 given of the aboVe-mentioned, and other fimilar phenomena, in feveral memoirs publifhed 

 previous to the year 1794. 



Cit. Venturi however, appears in fome degree to follow the opinion of Prevoft, fince 

 he aflerts that the volatility and odoriferous property of camphor are not qualities requifite 

 to produce the revolving motions which this fubftance exhibits when cut in fmall pieces 

 and caft upon water ; but that its volatility is neverthelefs neceflary for the continuance of 

 fuch revolutions. 



The motions of camphor, as I have proved in the memoir fo often quoted, and which is 

 inferted in the xxth vol. of the " Opufcules choifis de Milan," depend on two caufes, viz. 

 the extenfion of an oily fluid over the furface of the water, and on the rapid operation 

 (evaporation) of this fluid itfelf. 



When camphor cut in fmall pieces is thrown on the furface of the water, the inftanf 

 they touch this fluid they begin to move in a circular direflion, and run with rapidity in 

 different dire£lions ; but fhortly afterwards their motions decreafe, and the particles collect 

 in fmall heaps, which, though they have not an abfolute, have neverthelefs what may be * 

 called an inteftinal motion. All this takes place in confequence of the confumption of 

 the particles of camphor which form the fmall heaps ; for according to the former remarks 

 of Lichtenberg, as they necefTarily change their figure, they are compelled almoft every in- 

 ftant, being fubjeft to follow the attraftion of the mafs, which varies the conta£ts ac- 

 cording to their diverfity of figure. The water, by the attraflive power of its furface 

 eaufes the extenfion of the volatile oil of the camphor. This oil, by expofing a great fu- 



* Opufc. Sceiti di Milano, torn. XX. 



t Vide my Memoir " SulW attraxion di fuftrfids" Journal des Phyf, et Ann, di Chimic. Italiani, 

 torn. XVII. 



J; perficics 



