56 MOTIONS OF ODOROUS SUBSTANCES. 



If we pour upon the piece of linen, after having fpread it 

 ;upoft the plate, fome drops of water coloured with logwood, 

 this water runs off in coloured ftrcaks. 



The fame effects take place when we ufc a piece of fine 

 white paper, not fized. 



We obtain them equally with all the animal and vegetable 

 fubftances, with the faline liquids and folutions ; whether we 

 place them, under the fame circumflances, in contact with 

 each other, or with water. 



Thcfe phenomena take place not only upon a wet china 

 plate, but they are alfo obferved upon furfaces of pottery, and 

 many other fubftances. 



From thefe facls, and feveral others analogous to them, Ci- 

 tizen Prevoft draws the following inferences : 

 pcncral rcfults. i . That all liquids poflefs the property of mutually repelling 

 each other. 



2. Thiat all dry organifed fubftances, which preferve any 

 remains of organifation, exhale, whilft they imbibe water, an 

 elaftic fluid, which carries with it a part of this water, and re- 

 pels that which furrounds it upon a piece of wet glafs. 



The firft inference is contradictory to the general law of the 

 mutual attraction of the molecules of matter. 



As to the hypothefis of Citizen Prevoft, concerning the 

 formation of an elaftic fluid, we (hall remark, that, before he 

 attributes phenomena to new caufes, he ought to endeavour 

 to account for them by thofe which are already known ; to 

 diftinguifli the effects produced by odorous fubftances from 

 thofe prefented by inodorous ones ; and perhaps to eftablifh in 

 a more certain manner this repulfion of liquids by paper and 

 linen ; for this repulflon may very poflibly be nothing more 

 than an appearance produced by the flowing down of the 

 water upon the inclined furfaee which thefe fubftances raiie 

 around themfelves as they imbibe this liquid. 



XIII.— Cafe 



