290 
IMPEKFECTION OF THE 
Chap. IX. 
being separated from each other by wide intervals of 
time. When we see the formations tabulated in written 
works, or when we follow them in nature, it is 
difficult to avoid believing that they are closely con¬ 
secutive. But we know, for instance, from Sir E. 
Murchison’s great work on Eussia, what wide gaps 
there are in that country between the superimposed 
formations; so it is in North America, and in many 
other parts of the world. The most skilful geologist, if 
his attention had been exclusively confined to these 
large territories, would never have suspected that during 
the periods which were blank and barren in his own 
country, great piles of sediment, charged with new and 
peculiar forms of life, had elsewhere been accumu¬ 
lated. And if in each separate territory, hardly any 
idea can be formed of the length of time which has 
elapsed between the consecutive formations, we may infer 
that this could nowhere be ascertained. The frequent 
and great changes in the mineralogical composition of 
consecutive formations, generally implying great changes 
in the geography of the surrounding lands, whence the 
sediment has been derived, accords with the belief of 
vast intervals of time having elapsed between each 
formation. 
But we can, I think, see why the geological forma¬ 
tions of each region are almost invariably inter¬ 
mittent ; that is, have not followed each other in close 
sequence. Scarcely any fact struck me more when 
examining many hundred miles of the South American 
coasts, which have been upraised several hundred feet 
within the recent period, than the absence of any recent 
deposits sufficiently extensive to last for even a short 
geological period. Along the whole west coast, which 
is inhabited by a peculiar marine fauna, tertiary beds 
are so poorly developed, that no record of several sue- 
