278 ECONOMIC GEOLOGY 
in America, and at the advice of the Geological Survey 
special efforts were made to reach the untouched deep level 
oil beds in California; and wells have now been sunk there 
to depths of over 8300 feet. The increased yield made 
California the most prolific of the States, and led to a serious 
fall in the price of crude oil. California reached its maximum 
of nearly 263 million barrels in 1923 ; but its decline has been 
more than counterbalanced by increased yields from Okla- 
homa and Texas. Nevertheless, in September, 1926, the 
Federal Oil Conservation Board of the United States (Repori, 
pt. i, 1026, p. 6; and cf. p. 8) states that the oil available 
by flowing and pumping wells from the present producing and 
proven fields would only maintain the present output for 
six years, and that of the current production more than 
half comes from only 4 per cent. of the wells, which are for 
the most part only a year or so old, and from fields that have 
been discovered within the past five years. The life of the 
fields, it proclaims a matter of grave concern. 
TrE OricIN oF OrL—Success in search for petroleum is 
helped by a right conclusion as to its origin. Chemists have 
repeatedly asserted that mineral oil is an inorganic product, 
due to the action of superheated steam on iron carbides in 
the interior of the earth. This theory is a chemical possi- 
bility, but is disproved by the evidence of distribution. 
If the oil came from the interior it should be found mostly 
in old rocks and be rare in new rocks. The reverse is the case, 
Oil is not found in any commercial quantity in the most 
ancient rocks of the earth’s crust nor in the Cambrian. Ac. 
cording to Beeby Thompson (0il-Field Explor., i, 1925, p. 16), 
out of a total production to the end of 1923 of 12,094,000,000 
barrels, the Kainozoic yield was 44 per cent., the Mesozoic 
15 per cent., and the Paleozoic 41 per cent. Of the Palzo- 
zoic 88 per cent. is Permian and Carboniferous, 2 per cent. 
Devonian, and 10 per cent. Silurian and Ordovician. Hence 
the youngest geological Group yields most oil, and in the 
Palzozoic the upper Systems are the most productive, and 
there is practically none in the lowest, the Cambrian. 
Petroleum is an organic product due to the slow distillation 
of buried animal and vegetable tissues by heat and pressure. 
The organic nature of oil is suggested by its composition of 
carbon, hydrogen, and oxygen, which are the chief constitu-