242 
and overlying it a deep-sea formation of dense dark clay, capped 
after a long interval by clean bright sands. The materials of 
these beds are of course quite different, the proportion of iron 
and the condition of the iron different m each, each was not 
derived from its immediate predecessor, but from the disinte- 
gration of other rocks. The forces employed were, of course, 
analogous to all forces displayed before and since; but the 
phenomena are connected only by a law which embraces the 
whole of the diverse operations and effects. 
36. The lesson from the tertiary rocks is, that species ot rock 
and rock-formations, go on increasing with the age of the 
earth. There is no mark of a return to the simpler and fewer 
deposits of eozoic date. Cotta says, a they have been in- 
creasing continually ever since the first solidification ot the 
earth’s crust.” ^ 
37. We have thus hastily reviewed formations extending 
through eighteen miles of thickness, as developed at one place 
or another on the earth’s surface. They afford the strongest 
presumption against the theory of recurrence m a cycle. The 
force of the argument in question, and the nature of the 
evidence for progression by a law more deeply seated than the 
phenomena, is expressed in the variety of the great na ura 
successions into which the whole series is divided by charac- 
teristic differences. t We take the table from Professor 
Haughton : — - 
Thickness in feet. 
Eozoic 
Lower Silurian 
Upper Silurian 
Devonian ... 
Carboniferous 
Permian 
Triassic 
Jurassic 
Cretaceous ... 
Tertiary 
26,000 
25,000 
5,500 
9,150 
14,600 
3.000 
2,200 
4,590 
11,213 
9.000 
* Cotta, Rocks, p. 395. _ . 
t The argument against uniformitarianism was long ago admirably epito- 
mized by the insight and mental force of Professor Sedgwick, thus: “ If the 
principles I am combating be true, the earth’s surface ought to present an 
indefinite succession of similar phenomena. But as far as I have consulted 
the book of nature, I would invert the negative in this proposition, and affirm 
that the earth’s surface presents a definite succession of dissimilar phe- 
nomena .” —Anniversary Address, Peb. 1831. 
