of Cancer , and on Animal H fa tic Air . 4 1 7 
hepatic air. The following experiment proves, that a fub- 
ftance, which has very much the appearance of oil, is formed by 
the combination of fulpbureous hepatic air with fixed air and 
volatile alkali. 
A quantity of impure hepatic air was obtained by adding 
vitriolic acid to common liver of fulphur. When this fluid 
was agitated with lime-water, it produced a copious precipita- 
tion. It therefore contained a confiderable proportion of fixed 
air. One meafure of it was now introduced into a (lender 
graduated tube, inverted over mercury, and was mixed with an 
equal bulk of alkaline air. As foon as the airs came into contaft 
with each other, a white cloud was produced, the mercury 
began gradually to rife in the tube, and at the end of fix hours 
the air that remained occupied the fpace of only one meafure 
and one-third. The furface of the mercury within the tube 
firft became black, and a part of it afterwards acquired a red 
colour refembling cinnabar. In the courfe of the experiment, 
a yellowdfh oleaginous fubftance was depoflted upon the inte* 
rior furface of the tube. This fubftance, in fome parts of the 
furface, formed itfelf into globules ; in others, it was extended 
Into ramifications, having the refemblance of trees in minia- 
ture, and it gradually aflumed a deeper colour, till at length it 
acquired a greenifh caft. The fubftance, thus obtained, had a 
very fetid odour : it appeared to have a near refemblance to an 
animal oil which had become green by putrefadlion. It was, 
however, foluble in water, and the odour of the folution was 
increafed by the vitriolic, and deftroyed by the concentrated 
nitrous and dephlogifticated marine acids. 
Mr. Cruikshank, who affifted me in moft of the fore- 
going experiments, and on whofe accuracy 1 could place the 
greateft reliance, examined, in my abfence, the red and black 
Vo l. LXXX. I i i powders 
