48 
ON NAPHTHA AND ITS USES. 
stances are composed of 6 atoms of carbon and 6 atoms of 
hydrogen ; or in 100 parts, of 86 and 14, by Hess's 
analysis. 
Mineral petroleum seems to be very different in constitu- 
tion and qualities from the fetid, factitious tar, derived from 
the igneous decomposition of pit-coal. The latter, accord- 
ing to Mr. Mansfield, is resolvable into six different sub- 
stances, which he names alliole, benzole^ toluole, camphole, 
mortuole, and nitrobenzole. I do not believe that a series 
of similar bodies can be extracted from native bitumen or 
petroleum. Indeed, he himself informed me that the fluid 
bitumen now being pumped up so abundantly from the 
Redding coal mines in Derbyshire, of which I furnished 
him with a specimen, affords no such distinction of products, 
a result in accordance with my own experience. These 
differences between the natural, and factitious petroleums 
lead me to conclude that the former are not the result of 
igneous action, but of that of water upon carbonaceous 
matter in the mineral strata. In confirmation of which 
view it may be observed that not only in the above-named 
localities, but also at Monte Ciaro near Piacenza, at the 
Lake of Tegern in Bavaria, near Neufchatel in Switzerland, 
in the Department of the Ain in France, &c, the bitumen 
is accompanied with a copious flow of water, on which it 
floats, and from which it is skimmed. 
Petroleum of various shades, from the green of the Bar- 
badoes springs to the pale yellow of Amiano, has been long 
known to possess certain medicinal properties. The rock- 
oil of Barbadoes, or as it has been vulgarly but improperly 
called, Barbadoes-tar, has been found an useful stimulant 
to torpid bowels, promoting in such a temperament the 
alvine discharge. Its chief value, however, is as an exter- 
nal remedy in a variety of cutaneous affections. But petro- 
leum, either by itself, or combined with any of its solvent 
