62 View of fomc late Difcoveries and Improvement* 



able manner. Romieu afcribeel this phenomenon to eleclri- 

 city, but Volta has proved that electricity has no connec- 

 tion with it. Lichtenberg was of opinion, that camphor^ 

 lofing a great deal by evaporation, continually decreafes in 

 bulk, and that thefe fmall fragments of it change their con- 

 figuration, which makes a variation in their refpe£Uve at- 

 tractions. Volta thinks that the vapours which exhale from 

 thefe bodies ftrike the air and the water with fufneient force 

 to caufe the moleculre, from which thefe vapours are exhaled, 

 to be agitated as above mentioned. 



Brugnatelli has convinced himfelf that this phenomenon 

 takes place with all fubftar.ces that contain much eflential 

 oil, fuch as the leaves of laurel, fage, thyme, vanilla, the nut- 

 meg-tree, the rhus toxicodendron (the poifon oak), the rhui 

 •uernix (the noifon-afh). He found alfo that fmall bodies 

 which did not move on the water acquired that property 

 after being impregnated with eflential oil. A piece of bread, 

 for example, rubbed again (I a piece of lemon-peel and im- 

 pregnated with eflential oil of lemons, moved, after being 

 placed upon water a little warm. 



Thefe experiments prove that it is jets of eflential oil 

 thrown out with rapidity from thefe bodies, which make 

 them move on the water. Thefe jets experience a refiftance 

 from the air and the water, as a lighted rocket experiences a 

 refiftance from the air by which it is made to afcend ; that 

 is to fay, in a direction oppoflte to the jet of the flame. 



Venturi, who repeated all thefe experiments, made ieveral 

 fmall (licks of camphor, which he placed on water, adding to 

 them a bit of lead by way of ballad. They all moved as ufualj 

 but he obferved them become a little fmaller above the fur- 

 face of the water, and at length break in two. This eflccl: 

 is more fpeedy if the water be a little warm, and is occa- 

 fioned by the continual evaporation of the parts. 



Botany. — Though the number of plants is fo confider- 

 able, being eftimated at about twenty thoufand, that the moll 

 retentive memory can fcarcely remember their names, the 

 ardour for this branch of fcience does not feem to decreafe. 



6 U 



