506 CENOZOIC ERA— AGE OF MAMMALS. 



Eocky Mountains, and Appalachian, are represented, in order the better 

 to locate the lakes. It will be observed that the continent is nearly 

 finished. 



Europe is now remarkable for its inland seas. It was much more 

 so in Tertiary times. Many great cities, as, for example, London, Paris, 

 Vienna, are situated on Tertiary strata, partly because these strata are 

 usually found on the borders of continents, and partly because they 

 are often found in the course of great rivers, which once drained lake- 

 basins. 



Character of the Rocks. — The rocks of this period, along the At- 

 lantic border and in the interior Plains and Rocky Mountain region, 

 are mostly imperfectly lithified ; but on the Pacific coast they are not 

 only of stony hardness, but in many cases completely metamorphic. 

 Much of the rock in the Coast Chain is scarcely distinguishable from 

 the schists of the Palaeozoic or still older periods. The reason is evi- 

 dent — metamorphism is closely connected with mountain-making, and 

 mountain-making continued until the Tertiary on the Pacific coast. 



Coal, — Again, in the Tertiary rocks we find coal, although more 

 usually in the imperfect condition called lignite. We have already stated 

 that the Rocky Mountain coal-fields are by some referred to the Ter- 

 tiary. We have referred these to the Laramie. But there are others 

 about which there is as yet no controversy. The Coos Bay coal, of 

 Oregon, is probably Miocene-Tertiary. The Nevada coal is Upper Eo- 

 cene or Lower Miocene. Again, Mr. Selwyn, the Geologist of Canada, 

 has reported large fields of coal on the Qu'Appelle and the North 

 Saskatchewan Rivers, covering an area of 25,000 square miles, a part, 

 at least, of which he refers to the Tertiary. Much of this coal is of 

 good quality. It seems most probable, however, that this also belongs 

 mostly to the Laramie. 



In Europe also an imperfect coal (lignite) is found in the Miocene 

 in considerable quantity. 



Lava-fields. — The great lava-fields of the western part of the con- 

 tinent belong mostly to the Tertiary : (1.) The great Lava-flood of 

 the Northwest (already spoken of on p. 210), which covers Northern 

 California, Northwestern Nevada, a large part of Oregon, Washington, 

 and Idaho, and extends far into Montana and British Columbia. This 

 is one of the largest fields in the world. (2.) The lava-field of the 

 Coast Range of California, especially in Napa and Lake Counties, and 

 northward into Oregon. (3.) Enormous fields in the Plateau and 

 Basin regions. 



Life- System. 



General Remarks. — We have already spoken of the great and rapid 

 change in the life-system between the Cretaceous and the Tertiary, 

 even where the two series of rocks are continuous and conformable. 



