4 
MODERN GEOLOGY IN AMERICA 
which latter stream he floated to its mouth, near Prairie du Chien; 
thence down the Mississippi River to St. Louis. Subsequent jour¬ 
neys took him far up the Missouri and Arkansas Rivers. 
Nuttalhs fundamental observations in geology were the recog¬ 
nition for the first time in America of our great Carbonic System 
of rocks which include our immense coal reserves, and the discov¬ 
ery on the western continent of a second great rock sequence which 
we now call the Cretacic System. 
In the determinations of the presence of Carbonic rocks for the 
first time in North America Nuttall’s explanations refer mainly 
to the geological characteristics as they appear along the Missis¬ 
sippi River. He rather naively remarks that he is “Fully satis¬ 
fied that almost every fossil shell figured and described in the 
Petrifacta Derhiensia of Martin was to be found throughout the 
great calcareous platform of Secondary [Paleozoic] rocks exposed 
in the eastern part of the Mississippi Valley.” Thus by means 
of the organic remains alone he parallels these Mississippian Lime¬ 
stones with the Mountain Limestones in the Pennine Range of 
the north of England to which a number of years later Conybeare 
gave the title of Carboniferous — a name by which we now know 
them the world over. 
On his Mississippi venture, besides garnering great quantities 
of new and interesting plants and taking voluminous notes on the 
birds, this intrepid naturalist made extensive collections of the 
fossils which he found abundantly scattered through the limestone 
rocks, which in high cliflFs bordered both sides of the great stream. 
At this late day one can hardly appreciate the scantiness of the 
knowledge existing concerning the geological column a hundred 
years ago. 
When Nuttall arrived upon the scene lowa-land was indeed a 
veritable terra incognita. No scientist had before him laid eyes 
upon the field. Along the Mississippi River, as we now know, 
he collected fossils from rocks which were mainly, if not entirely. 
Early Carbonic in age. So his identification of forms was, with 
a few possible exceptions, doubtless correct. In this connection 
it must be remembered that at that time and for many long years 
afterwards the inferior rocks of not only this country but through¬ 
out Europe were entirely undififerentiated. The great successions 
of older stratified formations which were subsequently sticces- 
