232 GEKEKAL GEOLOGY. 



the western part of our own continent, which reveal the 

 fact that the strata containing the coal of these vast regions 

 are of much later geological age than the coal bearing strata 

 of Europe and America, which were known and studied as 

 coal-bearing strata up to within the past few years. These 

 Asiatic coals which are shown to be of Mesozoic age, consist 

 of both bituminous and anthracite varieties, and some of 

 their mines are the oldest coal-mines in the world. 



The coals of the western part of our own country are 

 probably of still later origin than those of Asia, just 

 mentioned, it being now reported that they are found in strata 

 of Tertiary age. These western coals have been generally 

 called lignite, but they show no more than, if as much woody 

 structure as our Iowa bituminous coals do. In view of all 

 these facts, not known to the earlier geologists, Prof. 

 Newberry justly remarks, " the question is suggested whether 

 the name given to the formation which contains the most 

 important European coal-strata has not been somewhat 

 hastily chosen. 



However, be that as it may, the coal-measure strata of Iowa 

 occupy the same relative position in the geological series that 

 those do to which the name was first applied, and to which it 

 was once supposed all the coal of the earth belonged. These 

 later discoveries then, need cause no misconception in the 

 mind of the student of Iowa geology when comparing it with 

 the ordinary classification of the text-books. 



The coal-measure group of Iowa is properly divided into 

 three formations, namely: the Lower, Middle, and Upper 

 coal measures, each having a vertical thickness of about two 

 hundred feet where it has been most fully studied, but they 

 probably all thicken to the southwestward. 



1. THE LOWER COAL-MEASURES. 



Area and General Characters. It is a matter of great regret, 

 that circumstances require the publication of this report 

 before this most important of all the geological formations of 



