Motions produced !>)< the Emavatloiis of Odorant Bodies. 'lee 



Kke thofe of the camphor, and difengages a fluid which prevents the water from pene- 

 trating the odorant fubftance. The motion ceafes, bdcapfe this fubRance is tlien plunged 

 in a fluid formed by the oil, which fluid is not air. 



l5. AW bodies which are not odorant prefent, when hot, t!ie fame phenomena as odorant 

 bodies. In faft, the heat gives tliem a degree of fmell. To this phenomenon our author 

 refers the bubbles and the motion, which are feen when an ignited piece of money is thrown 

 into water. The elaaic fluid is according to him the caloric, which. is difengaged in pro- 

 portion as the water penetrates the pores of the metal. It is neverthelefs much more 

 fimple to attribute this phenomenon to the water converted into vapour round the ignited 

 nietal,.and fometimes to hydrogene gas, when the metal is capable of decompofing water, 

 efpecially at this temperature. 



After the explanation of thefe experiments, Mr. Prevoa hopes with reafon that they will 

 contribute to the theory of odours, which fo nearly refembles that of the gafes. He doe» 

 not flatter himfelf with having exhaufted this fubjefl, but confiders his difcoveries as the 

 means of rendering odour perceptible by water not only to the fight but even to the touch, 

 as are likewife the vibrations of fonorous bodies. Men deprived of the fenfe of fmell, and' 

 even the blind, according to him, may in this manner diflinguifli odorant bodies from thofe 

 which have no fmell. « Perhaps," fays he, « tliis kind of odorofcope may, by improve- 

 ment, become an odorimeter. The exceptions, fuch for example as that of the cerumen 

 of the ears, which produces much effea on water without being perceptibly odorant, and 

 that of the fingers when hot or moift, are merely apparent ; for. If our fenfes do not in thofe 

 cafes difcover odour, thofe of animals more powerfully energetic, fuch as the dog, perceive 

 and diftinguifli individuals by its peculiar charafter. The odorofcope may afford the in- 

 formation which is wanting refpeding thefe effluvia. Thus it is that the fat of game, thj 

 fmell of «'hicli is nearly to us imperceptible, is very much fo to dogs, and exhibits fenfible 

 Burks by the odorofcope." 



Mr. Prevoft, who profefl"es much brevity in this memoir, affirms, that water placed on 

 the odorant liquor, inltead of this laft being put upon the water, affords a phenomenon 

 confiderably interefting, but which he has not defcribed. A fpeedy communication of the 

 reft of this interefting work is much to be defired. 



We fliaJl not in this place explain the manner in which it appears neceffary to confider 

 the principle of fmell, which no longer appears to us proper to be regarded as a peculiar 

 matter, and one of the immediate materials of vegetables, always identical, and enjoying the 

 fame properties. We {hall have occafion in future to enter more fully into this fubjea 

 and perhaps to reaify the notions which have hitherto been formed concerning the fpi-' 

 ritus reaor or aroma of plants. We fliall content ourfelves with obferving, that the 

 phenomena defcribed with clearnefs and precifion by Mr. Prevoft, as well as the theory he 

 has given, are referable to the attraaion of the odorant matter in the mafs for air and water," 

 and tlic folution which takes place in one or the other, or in both at the fame time. 



^2 IV. ^ 



