the growth of continents. 123 
isted, there was an age in the physical history of 
the world when the lands consisted of low islands, 
' when neither great depths nor lofty heights 
diversified the surface of the earth, — when both 
the animal and vegetable creation, however nu- 
merous, was inferior to the later ones, and com- 
paratively uniform in character, — when marine 
Cryptogams were the highest plants, and Fishes 
were the highest animals. And this broad state- 
ment holds good for the whole of that time, even 
though it was not without its minor changes, its 
new forms of animal and vegetable life, its varia- 
tions of level, its upheavals and subsidences ; for, 
nevertheless, through its whole duration, it was 
the age of low detached lands, — it was the age 
of Cryptogams, — it was the age of Fishes. From 
its beginning to its close, no higher type in the 
animal kingdom, no loftier group in the vegetable 
world, made its appearance. 
There was an age in the physical history of the 
world when the patches of land already raised 
above the water became so united as to form large 
islands; and thoi.gh the aspect of the earth re- 
tained its insular character, yet the size of the 
islands, their tendency to coalesce by the addition 
of constantly increasing deposits, and thus to 
spread into wider expanses of dry land, marked 
the advance toward the formation of continents. 
This extension of the dry land was brought about 
