Page:Popular Science Monthly Volume 79.djvu/427

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of the formations are not well exposed, and hence the number of seams of coal is not well known. The evidence suggests more than a dozen seams, varying in thickness from 6 inches to more than 35 feet. The Tokun formation overlies the Kushtaka conformably and consists of about 2,500 feet, chiefly of sandy shales, but containing also, sandstone and a subordinate amount of limestone. All the evidence thus far found indicates that the Stillwater formation is marine, the Kushtaka, non-marine, and the Tokun marine.

The structure of the rocks of the coal field is, in genera], monoclinal, the most prevalent strike being northeast: the dips are usually