132 IOWA ACADEMY OF SCIENCES. 



roots in the clay under the coal, nor was a case reported 

 by any of the miners interviewed. The clay floor is often 

 uneven. It may dip as much as five degrees when the 

 structure of the overljang clays shows that there has been 

 no folding. It is dotted with low, broad mounds at times 

 and is rarely level. 



The purity of some beds is very constant, while the 

 amount of ash in the lignite from others will increase ten 

 percent and even more in a lateral distance of two hundred 

 yards. So great a change in quality, however, is unusual. 

 Often the upper two or three feet, or even all of a thin bed 

 seems to have decayed, as though after the woody matter 

 had accumulated under water, the lake or swamp under 

 w^hich it was deposited had been partly drained and the 

 lignite exposed to the air for a time before it was covered 

 by silt. The ash in this "soft" lignite is often twenty per 

 cent and it is worthless as fuel. This is as apt to be true 

 of beds low in the Laramie as of those that are near the 

 top. 



It is difficult to formulate an hypothesis for the origin of 

 the lignite that is in harmony with all of the facts cited. 

 The ordinary explanation for coal deposits seems inade- 

 quate since nearly all of the phenomena on which it is 

 based are absent in this field. There are no roots in, nor 

 stumps rising out of the underlying clays; nor are there 

 delicate leaf prints preserved in the body of the coal, indi- 

 cating deposition in quiet water. Moreover, the flora of 

 the Laramie, or at least those forms that have been col- 

 lected from the lignite area and in close connection with 

 the lignite, are of genera which to-day live on dry ground. 

 Many of the beds seem to be made up entirely of wood, 

 with no addition of leaves or the finer forms of vegetation. 

 This wood has suffered so little decay that it is hard to 

 think that the material that forms the upper part of the 

 bed grew upon or derived nourishment from that below% 

 and where the beds are twenty feet thick, not an uncom- 

 mon occurrence, it is equally hard to conceive of trees 

 growing on ten feet or more of fallen but undecayed 

 trunks, and striking root down into the underlying clay. 



