On the Movements of' Camphor upon Water ^ 391 
This effect of the pellicle reminded him of that of a drop of 
oil, which, as Vpnturi observed, suddenly paralysed the mo- 
tions of the camphor, when dropped upon any part of the 
aqueous surface. Dissatisfied, however, with the explanations 
of this singular fact, M. Serulias supposes, that the camphoric 
emanation was dissolved by the oily substances expanded over 
the water, and that this dissolution taking place on every part 
of the chain, formed by the camphoric molecules, propagates 
itself more and more, and prevents the reaction which produ- 
ces the motion. The inactivity of camphor placed upon water 
impregnated with a fat matter, he explains in a similar man- 
ner. 
On the Motions of the Alloy of Potassium and Bismuth upon 
Mercury. 
This alloy moves with great volubility on a bath of mercury, 
whether it be covered with water or not. In both cases it 
exhales such a strong smell of garlic or phosphorus, that it 
cannot be ascribed merely to the small quantity of arsenic in 
the bismuth, but to a particular modification of the hydrogen 
produced. 
M. Serulias remarks, that during the decomposition of this 
alloy upon mercury, it forms at the surface of the bath a blacb 
pellicle, (found by analysis to be a mixture of the oxide of bis- 
muth and charcoal) ; that this pellicle is attracted by metallic 
substances, and not by those which are not metallic ; that if a 
plate or rod of zinc, iron, copper, brass, silver, or even bis- 
muth, touches the water of the bath, no attraction is exhibited, 
but that if it penetrates to the mercury, the black matter 
springs upon the metal with the rapidity of lightning, and even 
to a great distance, — a phenomenon which he ascribes to the 
electric state of the black matter. 
The agitation of the alloy of potassium and bismuth, does not 
appear to him to be owing to the amalgamations of the potas- 
sium, but to the disengagement of hydrogen, resulting from the 
decomposition either of the atmospheric water, whose accumu- 
lation round each fragment becomes instantly visible, or of that 
contained in mercury, more or less moist. 
