572 TJie American Naturalist. [July, 
it may flow to its goal, the sea, and so much of it stands about 
idly, instead of quickly running off, that it is in good part 
evaporated and carried away through the air. Evidently we 
have here to do with a geographic individual that is just entering 
Its career, that still retains its embryonic characteristics, so little 
has it advanced in its life-history. 
Can we not foretell something of the future history of this 
plain ? As the rivers carve their trenches deeper and deeper, 
and the enclosing slopes are wasted away and widen out, and 
the little side-gullies eat backwards and increase in length till 
they become ravines and the ravines grow into valleys, then the 
mter-stream surface, at first smooth and unbroken, is traversed 
in all directions by branching water-courses ; the rainfall is much 
more quickly led into the streams, — everything marks a more 
advanced stage, all of whose features are indicated in one of the 
models of the plain and plateau series. But we can not only 
predict the future of the Red River plains ; we can find examples 
of other plains, born at an earlier time, that are now in the 
advanced stage that the Red River plains have yet to reach. 
Look at the coastal plains of the Carolinas. They are the old 
bottom of the Atlantic, laid bare by a relative uplift of continent. 
They are well drained ; many streams run across them and many 
branches give ready discharge to the rainfall ; the channels are 
deeper below the general level of the country than are those of 
the Red River plains, and the inter-stream surface is much more 
broken; yet still enough of it remains to make it clear the 
present form is developed from an originally level, unbroken 
plain ; and a close comparison will leave no doubt that the coastal 
plains of the Carolinas differ from the Red River plains chiefly 
in being farther advanced in their cycle of development. They 
are closely related individuals, but they differ somewhat in age. 
They are like the egg of a caterpillar and the caterpillar itself ; 
not very similar at first, and not like what they will come to be 
later on, but closely comparable for all that ; their differences 
only manifest their relationship ; what one is, the other will be ; 
what the other is the first has been. Thus we can introduce 
mto geography the element of growth, that is, systematic change, 
