Story of the Mississippi-Missouri .— Claypole. 369 
may somewhat modify the statement above made. It is not 
impossible that during some time or at some epochs in the 
mesozoic era the waters of the Mississippi may have found 
their way into the wide channel to be presently mentioned 
extending from the gulf of Mexico to the Arctic ocean. The 
■course of the river was not separated from this body of water 
by more than about three hundred miles of land and this land 
possessed no very high ground to act as a watershed between 
them. There are some facts relating to the Mississippi delta 
which insinuate that the permanent outlet of the Mississippi 
into the gulf was not established until the western land had 
been elevated and in that case its former mouth must have 
been on the shores of the mesozoic channel or ocean to the 
westward. But on the other hand the Missouri is one of the 
last productions of the development of the continent. Its 
birth is a thing of yesterday when compared with that of its 
aged companion. Indeed it is scarcely out of its cradle. The 
Mississippi has long since worked its channel into shape and 
it now flows clear and steady. The Missouri is still employed 
in excavating a course for itself and its waters are laden with 
the clay and sand which it is removing from its bed. The 
Mississippi-Missouri—the greatest river-system on the globe— 
is made up of an old and a young stream but during all its 
■earlier history the older stream worked alone and only in 
days comparatively recent has it been joined and reinforced 
by its young and vigorous companion. 
The deposit brought down from the upper country by the 
•elder stream began to fill the head of the great gulf at its 
mouth and in this way to lengthen the course of the river. 
Before long the Ohio joined it and the two formed one delta 
reaching below the site of St. Louis. How far this process 
was carried on during mesozoic time we have no means of 
determining. But through all this time the Mississippi basin 
was washed by the waters of the great river and was contrib¬ 
uting of its substance to the formation of the delta. 
The long palaeozoic depression which came to an end in the 
•east at the close of the Carboniferous age seems to have con¬ 
tinued or to have set in again immediately afterwards in the 
west. For we there find that a wide arm of the sea extended 
up from near the mouth of the gulf already described that is 
from the site of the Texas of our day through the western 
