314. ANNUAL REPORT 
carbon as in coal, than we have in oil or gas. Or the decomposition could 
also have been stopped by a drying out of the shales—the presence of a 
certain amount of water being necessary for bacterial growth. Where 
animal remains in larger quantities were decomposed, we would have not. 
only the hydrocarbons, but also various nitrogen and sulphur compounds 
exactly as we find in limestone oils. 
“So that I should say that petroleum of the Pennsylvania type and 
gas in similar situations were formed in the mud of which shales were 
composed, from the time the mud was first deposited and by the decom- 
posing action of bacteria on the organic matter therein, and the formation 
continued until bacterial action was stopped in the ways above mentioned. 
“In the case of limestone oils and gas, the bacterial decomposition 
would begin with the deposit of the first dead organism, so that these sub- 
stances have arisen in such localities by the action of bacteria on the soft 
parts of those animals whose hard parts form the limestone. 
“Whether there is still undecomposed organic matter in shales, lime- 
stone, etc., experiment alone can determine; probably not, however. 
“Doubtless enormous quantities of gas and oil formed in the way 
above described escaped into the air and were lost, and what remained was 
retained in various mechanical ways which it is not my province to 
discuss. 
“My reasons for believing that oil and gas have arisen in this way 
may be summarized as follows: 
66 
I. Bacteria produce just these decompositions when acting in the 
absence of air. 
66 
_ “2, Bacteria were present in the formations along with other or- 
ganic matter. 
66 
3. Bacteria are the only agents known which can produce such 
decompositions except heat. 
“4. The action of heat (in the Ohio fields at least) is excluded by 
geologic evidence.” 
But were the fuels in question derived from organic matter which 
was once imbedded in the same rocks that now contain the oil and gas, or 
were the latter formed from organic matter which was deposited origin- 
ally in rocks lying beneath those now containing these substances? 
There are two different views on this matter, but the majority seems 
to favor the latter one. Dr. Orton regarded the oil and gas in the Tren- 
ton limestone to have been formed from animal matter which was en- 
tombed in that formation. In drilling wells in this the sand-pump some- 
times brings up masses of shells showing that the rock in places is highly 
fossiliferous, and the same fact has long been known from the study of 
outcrops of the formation in southern Ohio and other states. With such 
* 
