68 SECONDARY SERIES. 
and occupied by crowds of organic beings in 
the enjoyment of life.^ 
With regard to their adaptation to human 
uses, it may be stated generally, that the greater 
number of the most populous and highly civi- 
lize(i assemblages of mankind inhabit those 
portions of the earth which are composed of 
secondary and tertiary formations. Viewed, 
therefore, in their relations to that agricul- 
tural stage of human society in which man 
becomes established in a settled habitation, 
and applies his industry to till the earth, 
we find in these formations which have been 
accumulated, in apparently accidental succes- 
sion, an arrangement highly advantageous to 
the cultivation of their surface. The move- 
ments of the waters, by which the materials of 
strata have been transported to their present 
place, have caused them to be intermixed in 
* The secondary strata are composed of extensive beds of sand 
and sandstone, mixed occasionally with pebbles, and alternating 
with deposits of clay, and marl, and limestone. The materials 
of most of these strata appear to have been derived from the 
detritus of primary and transition rocks ; and the larger frag- 
ments, which are preserved in the form of pebbles, often indicate 
the sources from which these rounded fragments were supplied. 
The transport of these materials from the site of older forma- 
tions to their place in the secondary series, and their disposition 
in strata widely extended over the bottom of the early seas, seem 
to have resulted from forces, producing the destruction of more 
ancient lands, on a scale of magnitude unexampled among the 
actual phenomena of moving waters. 
