52 MOTIONS OF ODOROUS SUBSTANCES. 



than for the fmall portion of it which it has already diflblvcd 



and faturated ; it afcends along the folid piece, and there 



forms a curvilinear inclined furface. The fmall portion that 



is difTolved and faturated defcends along this furface, and, 



whilft it is defcending, it pufhes backwards, according to the 



laws of mechanics, the furface itfelf, and the folid piece that 



adheres to it." He thinks that we ought not to confound this 



effect with the repulfions which air impregnated with ether, 



or the exhalations of very hot camphor, exercifes upon the 



light bodies which are made to float upon the furface of the 



water. In this cafe only he admits the prefence of an elaitie 



fluid. ( Annates de Chimie, tome 21.) 



Dr. Carradori, a Dr. Carradori is of a different opinion : He explains this 



kind of oil. motion by the elective affinity of a fpecies of oil, which,. 



according to him, proceeds from the camphor in contact with 



the water. He believes that the retreat of the water, which 



takes place upon a wet china plate or piece of glafs, when 



camphor or other odorous fubflances are placed upon it, is the 



effect of the elective attraction of the furface of the plate or 



glafs for the oil which the fubftances emit ; and, according to 



him, it is this oil which caufes the water to recede, by fubfti- 



tuting itfelf in its place. (Annates de Chimie > tome 37 .) In 



fupport of his opinion, Dr. Carradori alledges, that camphor 



does not move upon the furface of the water when this is very 



limited. He has not been able to make fmall plates of metal 



move, as Citizen Pre volt had announced, by placing a morfel 



of camphor upon them, and letting them float upon the furface 



of the water. However, I have feveral times repeated this 



experiment, and always with fuccefs ; but it requires a great 



deal of care and extreme accuracy. 



New experi- Citizen Prevoft has replied to Dr. Carradori, in a Memoir 



mentsandobfer- w j,ich he has addrelfed to the Society, and which is intitled, 

 vattons oi Pre- lr ,> ™ , . , % r . ,,i. 



vo ft # JSourelks Lxperiences fur lea Mouvemais Jpontanes de dtverfes 



Subftances, a Vapproche ou an eontacle les unes des autres. The 



following are the principal facts which it contains : — 



Ether afts at a A drop of ether, placed upon a fmall plate of tin [fer blanc], 



diftance. 15 grammes (3| drachms) in weight, throws it into a lively 



motion, though it does not touch the furface of this liquid. 



Thus ether acts upon water at a dijlance. This fact may be 



verified in a very Ample manner. If we. place a fmall plate 



of 



