Miscellaneous. 327 



These water areas were of course at first salt ; but, as they had no 

 commumcation with the sea and received abundant supplies of pure 

 water fi'om streams and rains, they soon became fresh. They then 

 became the centres of rank vegetation, which either as moss filled 

 them up with its dense growth, or as large trees formed forests on 

 the shores. Later submergences covered all this material with a 

 heavy coating of mud-deposit, which now appears to us in the form 

 of strata of clay and sandstone rock. Thus was produced the coal, 

 which has played so important a part in human progress. So fre- 

 quent were the alternations of level that at one place in Nova Scotia 

 as many as seventy-six beds of coal separate as many strata of other 

 matei'ials, and the whole amount of deposit amounts to fifteen 

 thousand five hundred feet. As the elevating force became more 

 powerful, the amount of dry land increased, uiitU the lifting of the 

 Alleghany Mountains to a height of twenty thousand feet con- 

 cluded the process. 



Previous to this time vertebrated animals had been inhabitants 

 of water only, so far as the preserved remains have been discovered ; 

 but now air-breathers were introduced, which, instead of fins, 

 possessed limbs adapted for walking on dry land. These creatures 

 were all salamanders, and related to the frogs, beginning life in the 

 water and passing through a metamorphosis before reaching the 

 perfect state. 



The western regions were during this time occupied by a bound- 

 less ocean, whose western limit has not yet been ascertained ; and 

 such it continued for many ages, while the east was bringing forth 

 plant and animal each after its kind. The strata deposited in the 

 bottom of the western sea covered each other successively, so that 

 it is only the later chapters of the history that are now revealed to 

 us in the exposed beds of the upper formations. But the history of 

 the east Avas repeated. Its eastern coast-line rose and fell gradually 

 and islands appeared in the far west, heralding the birth of 

 another continent. Slowly the land areas extended, the western 

 growing from islands to a long narrow continent, honeycombed 

 with lagoons and lakes. The great central sea (now Kansas, Dakota, 

 &C.) contracted and finally lost its connexion with the ocean alto- 

 gether. The water areas, however, were for a long period brackish, 

 and brought forth oysters and other shell-fish of dubious proclivities, 

 capable of living in either salt or fresh water, but thrivang in a 

 mixture of both. The land was covered with a rich and dense forest 

 vegetation, and the bog-moss again encroached on the lakes ; but 

 the forest was in great contrast to that of the carboniferous period. 

 Instead of huge ferns and tree mosses we have the more highly 

 organized and beautiful forms represented by the existing deciduous 

 trees. Oaks, sassafras, magnolia, and poplar shaded a dense under- 

 growth of shrubs, while palms and some other tropical families di- 

 stinguished the general efiect from the familiar one of to-day. But 

 the moss ])erformcd its old function of coal-maker. Humblest 

 among jJants, its existence has l)0cn more important in world- 

 building than that of all the lords of the forest. Its masses died, 



23* 



