198 University Geological Survey of Kansas. 
oils. It will be seen by reference to that chapter that our 
Kansas oils are decidedly active optically, and, so far as this 
may have a bearing on the question in hand, there is strong 
evidence herein favorable to the organic origin of Kansas pe- 
troleums. 
It is believed by the writer that a careful examination of the 
various oil-fields in America, and even those of Russia and 
elsewhere, will reveal a series of complicated conditions which 
in general may be given a much more likely explanation by 
assuming that the oil and gas originated in the rock masses 
approximately where found than by assuming that they orig- 
inated at much greater depths. By this it is not meant at all 
that the oil in the Carboniferous sandstones in the Midconti- 
nental field originated in these same sandstones, or that the 
oil in the Trenton limestone of Indiana and Ohio originated in 
that limestone, but rather that the oil and gas of the Midconti- 
nental field originated principally in the great complex of sand- 
stones, limestones, and shales constituting the Coal Measure 
rocks of this area; that the oil and gas of the Trenton lime- 
stone originated in a like manner in the complex of stratified 
rocks in that vicinity, and so on, at least for a great majority 
of oil- and gas-pools now known. It should be remembered 
also that if there are two or more possibilities, likewise there 
may have been two or more methods of origin. Also, that if 
there are difficulties in accounting for the comparatively slight 
migrations of oil and gas in the Midcontinental field according 
to the organic theory, necessarily there must be much greater 
difficulty in accounting for similar migrations if one adopts 
the chemical theory. This latter statement is made with em- 
phasis, because no matter how they originated the question of 
their migrations within rock masses is one about which we 
know all too little and on which there should be a great deal 
of experimentation; but the difficulties of accounting for 
proper migrations are less by the organic theory than by the 
chemical theory. — 
