466 Catastrophism and Evolution. ' [August, 
exceedingly long periods of time, in order to explain the forma- 
tion of the crust of the earth in the simplest and most natural 
manner, by the means of the very same causes which are still 
active. Many geologists had previously imagined that the high- 
est chains of mountains which rise on the surface of the earth 
could owe their origin only to enormous revolutions transforming 
a great part of the earth’s surface, especially to colossal volcanic 
eruptions. Such chains of mountains as those of the Alps or 
the Cordilleras were believed to have arisen direct from the fiery 
fluid of the interior of the earth through an enormous chasm in 
the broken crust. Lyell, on the other hand, showed that we can 
explain the formation of such enormous chains of mountains quite 
naturally by the same slow and imperceptible risings and depres- 
sions of the earth’s surface which are still continually taking place, 
and the causes of which are by no means miraculous. Although 
these depressions and risings may perhaps amount only to a few 
inches, or at most a few feet, in the course of a century, still in 
the course of some millions of years they are perfectly sufficient 
to raise up the highest chains of mountains without the aid of 
mysterious and incomprehensible revolutions. ... We have 
long known, even from the structure of the stratified crust of 
the earth alone, that its origin and the formation of neptunic 
rocks from water must have taken at least several millions of 
ears. From a strictly philosophical point of view, it makes no 
difference whether we hypothetically assume for this process ten 
millions or ten thousand billions of years. Before us and behin 
us lies eternity.” This is even bolder than Hutton, who says: 
“TI take things as I find them at present; and from these I 
reason as regards that which must have been. .. . A theory, 
therefore, which is limited to the actual constitution of this earth, 
cannot be allowed to proceed one step beyond the present order 
of things.” 
The successive hypotheses which, linked together, form the 
chain of evolution are, first, the nebular hypothesis ; second, 
spontaneous generation; third, natural selection. It is omy 
with the last that geology has intimate relation. The general 
theory of a derivative genesis or the descent of all organisms 
by the various modes of reproduction from one or a few prim- 
itive types which came into existence by spontaneous genera- 
tion was believed long before the Darwinian theory was ad- 
vanced. Darwin’s great contribution was the modus operandi 
of derivative genesis. It was a mode of accounting for the m- 
