374 GEOLOGICAL SURVEY OF THE TERRITORIES. 



atmospheric circumstances, the fossil plants are, indeed, the written 

 records of the atmospheric and physical conditions of our earth at the 

 epochs which they represent. In the Marcellus shale of the Middle 

 Devonian, we see the first appearance of vegetation in the fossil remains 

 of large trunks of coniferous trees found here and there imbedded in 

 the shale, without any trace of branches or leaves. The shale also con- 

 tains a quantity of fish remains and large flakes of black, coaly matter, 

 apparently due to the decomposition of marine plants. It is an exten- 

 sive formation, sometimes a few hundred feet in thickness, impreg- 

 nated with bitumen, presenting everywhere the same characters. IsTo 

 other trace of land plants is left but these large fossil trunks. Where 

 was the land then just emerging for the first time from its marine cra- 

 dle 1 What was the aspect of the landscape % A black muddy surface 

 covered with an atmosphere darkened by vapors, where nothing is dis- 

 tinguishable, but perhaps at wide intervals, a group of some trees emerg- 

 ing from the muddy bottom and breaking the universal gloom. No 

 trace of animal life appears above the waters. All is dismal and silent. 



In the Upper Devonian, the Chemung, the Catskill group, and espe- 

 cially the red shale of the subcarboniferous measures, largely developed 

 in the anthracite basin of the Appalachian coal-fields, the remains of 

 land plants are more frequently found. These are not trunks of fossil 

 wood, but rather leaves and branches of a peculiar type of plants, ferns 

 with flabellate leaves, especially Noeggerathia, which we do not find in 

 the coal measures; and a few stems of Lycopodiacetv and Uquisetacece, 

 the first representatives of a class of plants which constitutes the largest 

 part of the vegetation of the coal. Leaves and branches of the Upper De- 

 vonian and subcarboniferous measures are compressed between layers of 

 shales, which bear ripple-marks, fissures caused by heat, and round prints, 

 evidently formed by drops of rain. If this does not indicate a succession 

 of seasons of different temperature, it shows at least a distinct atmo- 

 sphere, already penetrated by light, where changes of temperature cause 

 condensation or diffusion — rain, followed, perhaps, by some rays of sun- 

 shine. Animal life also appears at the surface; crustaceans and large 

 creeping saurians slowly plow their paths in the mud. Their traces have 

 been preserved upon the shales ; they indicate the first attempt at an 

 serial respiration. 



In the coal formations the aspect of the landscape is totally changed. 

 Everywhere the vegetable life predominates and attains its widest pro- 

 portions ; all still more or less under the influence of water. The emerged 

 land is marked by a succession of immense low swamps, whose surface 

 is concealed under a thick carpet of creeping plants, which fill them 

 with their debris. Where the land has already some fixity, immense 

 forests of large trees, mostly of the acrogenous kind, grow in a dense 

 mass, of a size and height which compare with the largest trees of our 

 time. They cover the land with a world of vegetation, which is scarcely 

 now conceivable, even by the wildest imagination. All the vegetation 

 is by its nature, its form, its texture, especially adapted to the absorp- 

 tion of atmospheric humidity and of carbonic acid. It is there at work 

 cleaning the atmosphere, in transforming into woody fiber its surplus of 

 water and of carbonic acid, and preparing it for animal life. For already, 

 remains of saurians, scorpions, insects of large size, found in the shale 

 of the coal, indicate that animal life has taken a marked place on the 

 surface of the land. There is there also an evident distinction of sea- 

 sons ; the layers of coal show annual decay and periodical deposition 

 of woody remains. 



The lower permian has still for its land vegetation many species of • 



