90 EH. ORTON—-GEOLOGICAL PROBABILITIES AS TO PETROLEUM. 
imentary rocks, before fishes appeared elsewhere in the world. The 
petroleum of the Trenton limestone owes nothing whatever to the verte- 
brate type, so far as its sources are concerned. 
While geologists find such warrant as I have indicated and much be- 
sides for believing in the organic origin of petroleum, it cannot be claimed 
that they hold concordant views as to the manner in which the conver- 
sion of organic tissue into mineral oil has been accomplished. They 
recognize the process as essentially chemical in its nature and are pre- 
pared to welcome ail pertinent facts and discoveries from students of this 
branch of knowledge. 
It is easy to see how the bituminous series may result from the de- 
structive distillation of either veeetable or animal substances enclosed in 
the rocks, and wherever conditions can be shown that provide for such 
distillation we are not obliged -to go further in our search. Destructive 
distillation can take effect on organic matter that has attained a perma- 
nent or stable condition in the rocks, like the carbonaceous matter of 
black shales or coal; but it seems improbable on many and obvious 
grounds that this can be the normal and orderly process of petroleum 
production. 
This production of petroleum must be in active operation in the world 
today ; at least it seems highly improbable that a process coeval with 
the kingdoms of life, growing with their growth and strengthening with 
their strength, a process that was certainly in its highest activity through- 
out Tertiary time, leaving a most important record in the rocks of that 
age, Should suddenly and completely disappear from the scene upon 
which it had wrought so long and upon which all other conditions appear 
to be substantially unchanged. 
What geologists would be glad to find in nature as matching to and 
harmonizing with the facts with which they are obliged to reckon would 
be a process in which the products of the organic world are transformed 
into mineral oil at ordinary temperatures and with complete consump- 
tion of the substances acted upon, so that no carbon residue would be 
left behind. They would also expect the transformation to be accom- 
plished while the organic matter still retained essentially its original 
character. 
The demands of the chemists are much the same. For the origination 
of the petroleum of Pennsylvania, one of them, namely, Professor HK. J. 
Mills, of Glasgow, Scotland, requires ‘“‘long continued application of a 
gentle heat to some derived form of cellulose.” 
Whether such a process as the geologists are looking for is a fact of 
nature and susceptible of satisfactory proof or whether the demand for 
it is mistaken and irrational remains to be determined. Once and again 
 Y 
