264 H. L. FAIKCHILD — GEOLOGY UNDER PLANETESIMAL HYPOTHESIS 



an inch or more in thickness and, so far as could be observed, having no 

 communication with other cavities. Certain pieces, when heated, allowed 

 the oil to escape through pores ; but others exploded violently when 

 heated. It is difficult to account for the oil in this rock by any artifi- 

 cial means such as ' salting.' To satisfy my own mind on this point, 

 however, I selected a place at some distance from the place where the 

 oil rock had been found, and dug into the dike ; oil-filled cavities were 

 found as in the original place. 



" The belief was entertaiued that the dike rock in some way picked 

 up the oil as it passed through some oil-bearing stratum. A well was 

 sunk between the two dikes to a depth of about 1,000 feet, but no oil 

 was found. Drilling was stopped in the Dakota sandstone. 



" It is somewhat singular that there should be cavities in the dike, 

 and still more singular that these cavities should contain oil. There is 

 no question that the oil is there, thoroughly sealed up in the basalt. 

 Pieces of rock which were dry and weatherworn were found saturated 

 with oil within. The oil seems to have been released only by decay of 

 the rock. The well indicates beyond doubt that the oil does not owe its 

 origin to deposits within 1,000 feet beneath the present surface. It is 

 furthermore difficult to conceive of this oil using the basalt dikes as con- 

 duits rather than the porous sandstones of the Dakota and Benton for- 

 mations which the dikes cut. It is equally difficult to conceive of fused 

 basalt picking up petroleum from an oil-bearing formation through 

 which it may have passed. It may be, however, that the pressure of 

 3,000 feet of rock, under some conditions, might keep the oil in a liquid 

 state even in contact with fused basalt. On the assumption that the 

 oil was of volcanic origin originally, as suggested by the new hypoth- 

 esis, its occurrence in the basalt dike is not so strange as it otherwise 

 appears." 



ISRAEL C. RUSSELLS' COMMENTS 



" Oxygen in the air. — On page 246 it is stated that the suggestion in 

 reference to the free ox}^gen in the air being due to the action of sun- 

 light on plants 'is opposed to the requirement in oxygen of the earliest 

 animal life.' This objection seems to lack force, since the earliest ani- 

 mals, as we are seemingly justified in assuming, must have subsisted on 

 plant food. The logic of events seems to require that algae long preceded 

 the appearance of animals on the earth, and did something in the way 

 of supplying oxygen, as well as furnishing food for the earlier faunas. 



" Volcanoes. — In the case of the parasitic cone on Etna, observed by 

 Fouque, cited on page 250, the evidence does not seem conclusive, so far 

 as I have been able to learn, that the vent in question had a direct com- 



