Editorial Comment. 371 
is complicated, but not upon a small scale. Actual exposures, 
though isolated, always furnish a check upon such work. 
EDITORIAL COMMENT. 
SOME RECENT SPECULATIONS ON THE ORIGIN OF PETROLEUM. 
The distinguished Russian chemist Prof. Mendeleef of St. 
Petersburgh, has recently discussed from a new standpoint this 
oft-mooted question and as considerable currency has been 
given to his theory, this fact, together with the eminence of its 
author as a chemist, renders some notice of it appropriate to 
these pages. 
In his essay Prof. Mendeleef sets out with the statement that 
most writers tacitly assume that petroleum is a product of 
vegetable matter. For this assumption there is, he says, no 
ground unless we admit that its chemical composition — re- 
sembling coal so closely as it does — may be admitted as an 
argument. This origin he sets himself to disprove. Petrole- 
um could not, he says, have been produced on the surface 
because it would have evaporated. Nor could it have been 
produced over a sea-bottom because it would have floated up 
and have passed off. Thirdly, he maintains it must have been 
formed where it now exists, because it could not have been 
transported as sand or clay, and could not have flowed on the 
surface. 
Now with all respect to the eminent attainments and bril- 
liant reputation of Prof. Mendeleef we may say at once that 
this catalogue does not by any means exhaust the list of pos- 
sibilities. There are situations in which petroleum may have 
been made other than the surface and the sea-bottom. Indeed, 
we have never heard the former advocated by any one. And 
granting, for the sake of argument, that petroleum can not be 
transported very far, yet Prof. M. adduces no satisfactory evi- 
dence against its formation in the region in which it actually 
occurs. 
We must assume that Prof. M. has some practical acquaint- 
ance with the geology of the Baku oil-regions of Russia but we 
can not refrain from suggesting that he does not show the 
familiaritv with similar districts in North America that would 
