412 Reviews — United States Geological Surveys. 



fossils wliicli it contains (Cycads, Ferns, etc.), it is supposed of tlie 

 age of the commencement of the Lias, and hence to com^e between 

 the Coal-beds and the Eed Sandstone : petrologically, much of the 

 Hor Sandstone is indistinguishable from some of the grits of the 

 Coal-bearing strata. Above these latter come the Cretaceous beds. 



The Coal-bearing beds contain clay-iron-ore and some very good 

 refractory clays. The beds of Coal themselves vary from less than 

 a foot to three or four feet. There are several beds in the section, 

 but denudation seems to have removed some of them in different 

 localities, so that few are worked in any one place. The thickness 

 of the formation varies much ; in one place they bored 600 feet 

 without getting out of the Coal-beds. The shafts are mostly shallow, 

 and the beds much interrupted by small faults. 



The most important locality in a Coal-producing point of view is 

 Hoganas; only two seams, however, are much worked there, viz. 

 the two lowest in the formation ; higher up the beds get poorer. 

 The dip of the Coal-strata is mostly at a very low angle, or nearly 

 horizontal. The quality of the Coal seems to differ much ; even in 

 the same bed there may be two or three kinds separated by thin 

 partings ; the better sorts are said to be quite as good as English 

 Coal for most economic purposes. The method of working has been 

 by pillar and stall, but of late the long wall system has been intro- 

 duced. In 1871 the output from the four chief localities was 

 1,992,590 cubic feet. 



The precise age of these Coal-beds is not quite settled. Prof. 

 Hebert considers them of the age of the Lias. Aniotig its fossils 

 are, Amjyhidesma donaciforme, PhilL; Avicida meqmvalvis, Sow.; 

 Pecopteris Beclcii, Brongn.; and Cycads. Prof. Torell notices the 

 affinity of the flora to that of the Yorkshire Jurassic beds, and 

 mentions the occurrence of Solenites Murrayana, L.. and. H. 



I?, IB "V IIE "W" S . 



L — United States GEOLOsicAii Suevets. 



1. Eeports of the United States Geological Survey of the Tierritories 



for the Years 1867-69. Eeprint, 1873. 



2. Eeport of the Geological Survey of Wyoming and Portions of 



Contiguous Territories. 1871. 

 o. Final Eeport of the Geological Survey of Nebraska and Portions 

 of the Adjacent Territories. 1872. 



4. Sixth Eeport of the Geological Survey of the Territories, embracing 



Portions of Montana, Idaho, Wyoming, and Utah. Washington, 

 1873. 



5. Contributions to^ the Extinct Vertebrate Fauna of the Western 



Territories. By Joseph Leidy. Washington, 1873. 



THE above volumes form only a portion of the results of the Survey 

 under the direction of Pro'f. F. V. Hayden, but they fully attest 

 the energy and zealous co-operation which has been brought to bear 

 on the Survey by himself and his able colleagues, since its com- 

 mencement in the present form in 1867. We have previously noticed 



