GEOLOGIC FORMATIONS OF NEW YOKE 169 



The fossils of the coal measures are almost entirely vegetable. 

 In the slates above the coal seams, most perfect and beautiful 

 impressions of leaves occur in profusion; and large trunks or 

 stems are found, almost always compressed to a thickness of only 

 an inch or two, though two feet or more in width. The greater 

 part of these trees seem to have been allied to the tree-ferns of 

 tropical climates, though there are remains of coniferous trees 

 and several other vegetable families. The character of this fossil 

 vegetation would seem to indicate that at the time it grew, a far 

 warmer climate than that now known prevailed over the tem- 

 perate and arctic zones. 



The fact that coal is of vegetable origin, seems to explain why 

 the lower rocks which form the state of New York contain no 

 coal. They appear to have been formed before terrestrial vegetation 

 flourished to an extent sufficient to form accumulations of this sub- 

 stance. 



The first relics of land plants are found in the Upper Silurian ; 

 above this they become more numerous and in the Catskill group 

 of the Devonian are quite abundant, forming occasionally minia- 

 ture coal seams an inch thick. 



In the Carboniferous rocks they increase suddenly to an enor- 

 mous quantity, and in later formations are .found in considerable, 

 but generally in less abundance. Coal is also found in newer 

 rocks, such as the Jurassic, Cretaceous and Tertiary. The coal 

 or lignite beds of the central part of the continent near the Rocky 

 mountains, belong to the Cretaceous and Tertiary rocks. The 

 coal of Vancouver-island on the Pacific coast is Cretaceous. The 

 coal beds near Richmond, Virginia, are of Triassic age. The con- 

 clusions to be drawn from our present knowledge are that good 

 coal is found above the Carboniferous system, but never below it. 



Permian 



This formation which is well developed in Europe, taking its 

 name from the Province of Perm, in Russia, is not known to exist 

 in New York state. It occurs in Texas and its vicinity. It has 

 been suggested that some of the uppermost deposits commonly 



