243 
38. In the present inquiry we have only for our guide the 
actual constitution of things. It may therefore be urged, look- 
ing at this alone, that succession is a necessary result of matter 
and force. But a consideration of the various facts above 
referred to may certainly allow, and probably does encourage, 
our concluding, with at least equal plausibility, that things might 
have been otherwise. Evolution may be a necessary product of 
matter and force ; but evolution in a particular direction is not, 
or may not be, a necessity. The variety of the changes indicated 
in the table, look as if the ultimate determining force was not 
necessity of any kind. 
EARTH MOVEMENTS. 
39. Mountain-chains are elevations of portions of the earth's 
crust, occasioned by lateral pressure springing from contraction 
of the nucleus. This elevation has taken place during all 
epochs of the geological succession save the present. We must 
presume either that the rate of cooling no longer produces con- 
traction, or that its force is exhausted elsewhere than at the 
surface. The modern phenomena which represent the ancient 
upraising of the strata are too minute for comparison. Since 
the tertiary there are no marks of extensive dislocations. 
40. In like manner denudation has removed enormous masses 
of all the ancient formations, sometimes planing off thousands 
of miles of deposits. The older denudations are more wide and 
deep than the more modern. There are proofs (according to 
1 rofessor Ramsay*) of the intervention of a vast lapse of time, 
during which this destructive work went on, between the funda- 
mental Laurentian gneiss of Scotland and the overlying Cam- 
brian slates; of a second interval between the latter and the 
Lingula flags; and so between these and the Tremadoc slates- 
between the last and the Llandello rocks; again, before we 
come to the Llandovery, and before we come to the Wenlock • 
and so down through the geological scale these dark spaces are 
repeated, ien such physical breaks are enumerated, and many 
more might be named. These, though they occur in a series, 
yet are so diverse in their duration, extent, and power, so 
obviously unconnected with anything in the structure of the 
strata themselves, that we must attribute their occurrence to 
some appointment of which we see the effects but cannot discern 
the cause. They are not the products of matter and time con- 
jointly ; for, as the Duke of Argyll pithily observes, “ Time does 
nothing by itself except by the*aid of its great aRy For 
rce. f 
* Quarterly Journal of the Geological Society, May, 1863 . 
t Quar terly Journal of the Geological Society, vol. xxiv. p. 272 . 
