ORIGIN OF CERTAIN FEADURES OREO ME BS iNS: 
Wuite the general theory of the formation of coal has long 
been worked out and accepted, it cannot be said that the details 
of the process are as yet altogether understood. Numerous 
puzzling phenomena are constantly encountered in all coal 
regions. In some regards Iowa is a particularly good field in 
which to work out certain of these points. The coal seams here 
are relatively thin and lie near the surface. The region has not 
been disturbed by mountain-making forces. The seams, with 
one or two exceptions, are not of great areal extent as is 
common in certain other fields, but are usually quite limited. 
Indeed it is frequently possible to find the whole of a seam in a 
single exposure and to be able to trace it readily from one limit 
to another. Thus the coal beds are reduced to the lowest terms 
and so become miniature representations of larger coal basins. 
They serve as models and present opportunities for investigation 
of certain phases of their structure which in larger basins have 
been obscured. 
In the following paper an attempt is made to explain a few 
of the different questions which arise in the study of coal beds. 
The observations were made on the beds of the Iowa-Missour1 
field alone, and the explanation is only offered as true of certain 
of these beds. Whether it is of value in other fields or not can- 
not be told; to workers elsewhere it may perhaps be of suggestive 
interest. 
There is probably no peculiarity of the coal seams of this 
region which is more constant than what has been called their 
basin character. In any individual bed the coal is not every- 
where of the same thickness; neither does it all lie at the same 
level. These two variations have usually a constant relation to 
each other, it being commonly true that the thinner coal is found 
at the higher points in the seam and the thicker hes in the lower 
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