THE LAWS OF GEOLOGICAL ACTION. 3 
theories to explain the common phenomena of the material 
universe ; and most of these theories, however varied in their 
details, turn out on examination to have a common root, and 
to be based on the same elements. Modern geology has its 
own theories on the same subject, and it will be well to glance 
for a moment at the principles underlying the old and the new 
views. 
It has been maintained, as a metaphysical hypothesis, that 
there exists in the mind of man an inherent principle, in virtue 
of which he believes and expects that what has been, will be ; 
and that the course of nature will be a continuous and unin- 
terrupted one. So far, however, from any such belief existing 
as a necessary consequence of the constitution of the human 
mind, the real fact seems to be that the contrary belief has 
been almost universally prevalent. In all old religions, and 
in the philosophical systems of almost all ancient nations, the 
order of the universe has been regarded as distinctly unstable, 
mutable, and temporary. A beginning and an end have always 
been assumed, and the course of terrestrial events between 
these two indefinite points has been regarded as liable to con- 
stant interruption by revolutions and catastrophes of different 
kinds, in many cases emanating from supernatural sources. 
Few of the more ancient theological creeds, and still fewer of 
the ancient philosophies, attained body and shape without 
containing, in some form or another, the belief in the existence 
of periodical convulsions, and of alternating cycles of destruc- 
tion and repair. 
That geology, in its early infancy, should have become im- 
bued with the spirit of this belief, is no more than might have 
been expected ; and hence arose the at one time powerful and 
generally-accepted doctrine of “ Catastrophism.” That the 
succession of phenomena upon the globe, whereby the earth’s 
crust had assumed the configuration and composition which 
we find it to possess, had been a discontinuous and broken 
succession, was the almost inevitable conclusion of the older 
geologists. Everywhere in their study of the rocks they met 
with apparently impassable gaps, and breaches of continuity 
that could not be bridged over. Everywhere they found them- 
selves conducted abruptly from one system of deposits to 
others totally different in mineral character or in stratigraphical 
position. Everywhere they discovered that well-marked and 
easily recognisable groups of animals and plants were succeeded, 
without the intermediation of any obvious lapse of time, by 
other assemblages of organic beings of a different character. 
Everywhere they found evidence that the earth’s crust had 
