545 
1877J Notices of Books. 
the lineal descendant of the group which immediately preceded 
it in point of time,” and being “ more or less fully concerned 
with giving origin to the group which immediately follows it,”-— 
he yet reminds us that “ from one point of view there is a truth 
in catastrophism which is sometimes overlooked by the advocates 
of continuity and uniformity. Catastrophism has, as its essen- 
tial feature, the proposition that the known and existing forces 
of the earth at one time adted with much greater intensity and 
violence than they do at present, and they carry down the period 
of this excessive adtion to the commencement of the present 
terrestrial order. The Uniformitarians, in effect, deny this pro- 
position, at any rate as regards any period of the earth’s history 
of which we have adtual cognisance. If, however, the ‘ nebular 
hypothesis ’ of the origin of the universe be well-founded, as is 
generally admitted, then, beyond question, the earth is a gra- 
dually cooling body, which has at one time been very much 
hotter than it is at present. There has been a time, therefore, 
in which the igneous forces of the earth, to which we owe the 
phenomena of earthquakes and volcanoes, must have been far 
more intensely adtive than we can conceive from anything that 
we can see at the present day. By the same hypothesis the sun 
is a cooling body, and must at one time have possessed a much 
higher temperature than it has at present. But increased heat 
of the sun would seriously alter the existing conditions affedting 
the evaporation and precipitation of moisture on our earth,, and 
hence the aqueous forces may also have adted at one time more 
powerfully than they do now. The fundamental principle of 
catastrophism is therefore not wholly vicious ; and we have 
reason to think that there must have been periods — very remote 
it is true, and perhaps unrecorded in the history of the earth— 
in which the known physical forces may have adted with an 
intensity much greater than diredt observation would lead us to 
imagine.” 
The truth in these remarks is undeniable ; but it strikes us 
that the difference between these two conflicting views resolves 
itself after all into the question, When was the “ commencement 
of the present terrestrial order ?” Catastrophists admit that the 
world is now governed by law, and that we find merely gradual 
change, and no evidence of arbitrary intervention, of alternating 
miracles of destruction and re-creation. But can they fix the 
date when the “ now ” began ? On the other hand, Uniformita- 
rians are quite willing to admit that in the pre-geological ages— 
which, as Dr. Nicholson intimates, have passed “ unrecorded in 
the history of the earth ” — all agencies whose effects we now 
witness must have been far more powerful than at the present 
day. But in admitting this we urge that the decline of such 
forces must have been very gradual, that the difference between 
then and now must have been in degree and not in kind, and that 
consequently, as the author shows, the history of the earth has 
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