196 University Geological Survey of Kansas. 
overlying a gas-sand with from 20 to 60 feet of shale between 
the two sandrocks. Here the flow of gas is stronger than at 
either place just named. Some of the oil-wells have gas enough 
in them to make them flow for a time without having the drill 
reach the gas-sand below, but the gas pressure is so enormously 
great and the wells are so strong that, should a gas-well be 
brought in without casing off the oil above it would drive the 
oil into spray in a very different manner from the compara- 
tively mild flowing properties possessed by such wells as do 
actually flow. Here, then, is another instance of a sandstone 
being filled with a gas underlying a second sandstone filled 
with oil, with what would seem to be positive evidence that no 
passage-ways whatever connect the two. How, now, can it be 
possible that both of these materials came from great depths 
below? 
It may be stated here that different men at different times 
have believed that the oil and gas of this Midcontinental 
field originated in deeper lying Silurian rocks, and have tried 
to explain the same by the assumption that a certain series of 
vertical fissures provided escaping channels for the oil and 
gas manufactured below. In fact, considerable money has 
been spent in prospecting based on this belief. Wells have been 
located where, according to such parties, they would be most 
likely to catch the oil in its upward migration. Unfortunately 
all such attempts have been unsuccessful, although a good 
many thousands of dollars have been spent. 
In the Russian oil-fields, already referred to earlier in these 
pages, oil and gas occur in a loose, uncemented sand of the 
Tertiary age. Mr. A. Beebe Thompson, in his most admirable 
book, The Oil Fields of Russia, has given us a good descrip- 
tion of the details under which oil and gas exist. He has 
reached the conclusion unequivocally that; for this most won- 
derful of all oil-fields, the hydrocarbons were produced in sands 
practically where now found. Ina lengthy discussion he shows 
how organic matter may have been imbedded in the sand be- 
neath the ocean-water, and under the influence of anerobic 
bacteria decomposition would take place, breaking down the 
complex organic molecules, producing the simpler molecules 
of oil and gas. : 
Another series of observations world-wide in extent may be 
mentioned. In our mining operations explodable gases are al- 
most universally present in coal-mines, the only mines we have 
