10 
HAROLD’S DISCUSSIONS. 
Illinois—in fact, all around the edge of dumber 7. 
Southward these strata dip beneath the more recent, 
and therefore they are themselves the older. The 
fossils found in them also show that the rocks belong 
to an earlier age, as they clearly indicate a warmer 
climate. The Gulf must have extended over all this 
region during this age, and there must have been also 
an inland fresh-water sea in western JN^ebraska, with 
arms spreading north perhaps as far as Oregon and 
west to California. Near the Atlantic from New 
Jersey south extends a strip of Number 6 a hundred 
miles wide. As the rock is comparatively soft, water 
erodes it easily, and the rivers flowing east from the 
mountains contain cascades which afford natural facili¬ 
ties for cities; hence there are Richmond, Raleigh, 
Columbia, Macon, and Milledgeville in this “Fall 
line ” belt. 
Still farther north than Number 0 we find in east¬ 
ern Kansas, Nebraska, and part of Dakota, a chalky 
rock formation which, from its position and fossils, 
we know is still older than Number 6. This we call 
Number 5. The region must have been under water 
during this age. About the boundary of formation 
Number 5 and extending beneath it, another forma¬ 
tion crops out on the surface in Iowa, Illinois, Michi¬ 
gan, Tennessee, and neighboring States. This (Num¬ 
ber 4) contains large and important beds of soft coal, 
and in its formation extended through a long period 
of warm, nioist climate. Beneath the coal strata and 
cropping out around them is another stratum, Num¬ 
ber 3, found in Illinois and Iowa. It abounds in curi- 
