GEOLOGICAL SURVEY OF THE TERRITORIES. 375 



plants of the coal-measures, but here the conifer appears, represented 

 for the first time by their leaves and branches, and are of a peculiar 

 order. The carboniferous vegetation loses its force by the disappear- 

 ance of its arborescent acrogenous plants. The debris are no more 

 heaped in immense deposits, but scattered here and there in the shales, 

 or forming by their agglomeration mere flakes of coal. This indi- 

 cates an atmosphere already discharged of greatest part of its carbonic 

 acid and of vapors. The triassic, which, with us at least, touches, by 

 the character of its flora, to the Jurassic, has plants which, like Cycadece, 

 rather indicate a warm than a vaporous atmosphere. But for this and 

 the following formations, the Jurassic, the data furnished by fossil 

 plants on this continent are too scant to permit reliable conclusions. 

 We have to pass to the lower cretaceous to find abundant remains of 

 laud plants, and here at once we have a vegetation absolutely different 

 in its characters from all that has been seen before. All the forms (the 

 needle form of leaves) which indicate atmospheric humidity, have dis- 

 appeared ; scarcely any conifers remain, very few ferns, no trace of 

 Lycopodiacece, but leaves of dicotyledonous plants, representing already 

 most of the genera of trees found in our forests. The vegetation is 

 therefore of a kind known to us. The atmospheric circumstances are 

 then analogous to those of our time. We now follow through the 

 cretaceous and tertiary formations merely modifications of species, 

 disappearance of some forms, reappearance of others, about as we 

 should have to do now in studying our flora in passing through a few 

 degrees of latitude*. 



THE FOSSIL PLANTS IN RELATION TO OUR PRESENT CIVILIZATION. 



To say that fossil plants have a relation to our present civilization 

 appears at first sight a paradoxical affirmation. But what is coal ? A 

 mere agglomeration of petrified debris of plants. And who at our time 

 could refuse to admit the influence of coal upon our actual civilization"? 

 Coal is the great generator of heat, of steam, of force,* a potent auxiliary 

 to every kind of enginery. It helps to the construction of our rail- 

 roads; it brings them to countries which, without it, would remain 

 deserts; and transports everywhere, with lightning speed, not only the 

 necessaries of life, but the products of industry essentially due to its 

 active cooperation. Coal is now used everywhere, and is the friend of 

 everybody. It has become an object, not of mere commodity, but of 

 absolute necessity. 



The formation of the coal is now pretty well understood among geol- 

 ogists. It results from active growth of woody plants, whose debris, 

 falling every year, are preserved against decomposition by stagnant 

 water, or great atmospheric humidity. It is the process which now 

 still forms our deposit of peat. It demands for its favorable action a 

 ground or basin, rendered impermeable by a substratum of clay, a pecu- 

 liar kind of plants, constantly growing at the same place, and heaping 

 their debris for a length of time. At our epoch the formation of peat 



* In the geological report of Dr. F. V. Hayden on the explorations of the Yellow- 

 stone River, under the direction of Brigadier General W. F. Raynolds, published in 

 1869, Dr. Newberry has clearly exposed the character of the vegetation in relation to 

 each geological epoch. 



