Motions produced hy the Emanations of Odorant Bodies. 1 53 



and continued to increafe till the evening of the 14th, when it was more violent than any 

 thing of tlie kind I had ever been witnefs to before, and continued till the evening of the 

 1 6th, without the leafl intermiflion. Our tents were all blown down, and we were under 

 the neceffity of fortifying our camp by driving polls near to each other firmly into*he 

 ground on the windward fide, and filling up the vacuities with bufhes in the form of an 

 hedge. During the continuance of this wind we frequently obferved fmall black clouds 

 •lianging over the lake : they had but little velocity, and were fometimes exhauRed, and dif- 

 appeared without reaching the fhore. 



From the large bodies of timber blown down about the lakes, it appears that hurricanes 

 are not uncommon. Coxe obferves in his Travels through Ruffia, that the lakes in that 

 country are fubjeft t,o terrible ftorms. 



III. 



Extrncl of a Alemoir of M. BENEDICT Pj!£rOST, of Geneva, on the Emanations of Odorant 

 Bodies. By Citizen FouRCROr*. 



VJlTIZEN Due la Chapelle, DireiSor of the Society of the Sciences and Arts at Mont- 

 auban, in the department of Lot, has forwarded to the Firft Clafs of the Inftitute, in the 

 name of the Society, a Memoir of M. BenedidlPrevoft, of Geneva, concerning various means 

 of rendering the emanations of odorant bodies perceptible to the fight. The Firft Clafs of the In- 

 ftitute heard the reading with great intereft at its fitting of the l6thPluviofe, in the year 5. 

 The following are the fa£ls configned in this Memoir : 



1. A concrete odorant fubftance, laid upon a wet glafs, or broad faucer, covered with 1 

 thin ftratum of water, immediately caufes the water to recede, fo as to form a fpace of 

 feveral inches around it. 



2. Fragments of concrete odorant matter, or fmall morfels of paper or cork, impregnated 

 with an odorant liquor, and wiped, being placed on the furface of water, are imme- 

 diately moved by a very fwift rotation. Romieu had mads this obfervation on camphor, 

 und erroneoully attributed the effefl; to eledlricity. The motion was perceptible even in 

 pieces of camphor of feven or eight gros. 



3. An odorant liquor being poMred on the water ftops the motion till it is diffipated by 

 evaporation. Fixed oil arrefts the motion for a much longer time, and until the pellicle 

 it forms on the water is taken off. 



4. When the furface of the water is cleaned by a leaf of metal, of paper, or of glafs, 

 plunged in and withdrawn fuccelfively until the pellicle is removed, the gyratory motion 

 is renewed. If a piece of red wax or of taper be dipped in water, and the drops fliaken 

 off into a glafs of water containing odorant bodies in motion, the movement will be ftoppcd. 

 The fame effeifl; is not produced by metal. 



5. An atmofphere of claftic fluid is formed round odorant fubftances, and is the caufc 

 of the circ£ls here defcribcd. 



6. A morfcl of camphor plunged to the depth of three or four lines in water, witliout 

 floating, excites a riiovcmcnt of trcpi<lation in the furrounding water, which repels fmall 



* Annalcsde Cliimii:, XXI. !C4 — Tranll.iuon. N. 



Vol.. I. — July 1797. X bodies 



