310 
this very same subject, which he had brought before them from 
time to time, many years before the investigations now referred 
to were undertaken. 33 He also added, “ That he believed that 
geological science was on the eve of a great revolution. 33 — • 
In the anniversary Address of Mr. Hamilton, President of the 
Geological Society last year, he made the following observa- 
tions : — 
“ Recent investigations have upset the ancient theories. It 
was formerly supposed that the crystalline rocks, particularly 
granite, owed their origin to igneous action. Now, it is well 
known that these granites are chiefly arranged in layers. The 
granite passes into gneiss, and the gneiss into mica schist and 
talc schist, and this is again closely connected with the green 
and grey slates ; and it is well known that many of these rocks, 
formerly considered as plutonic, are really metamorphosed 
rocks. 33 
These remarks refer principally to the order of the structure, 
and notice that granite is divided into bands, and changes into 
the slaty structure, as was described in my sections, and 
explained in my papers written in 1837 and since. 
I shall now quote Mr. Hamilton's observations, in his last 
annual Address, with reference to the igneous theory, which I 
had opposed for so many years, and which at length is being 
given up as untenable : — 
“ Another point,” observed Mr. Hamilton, “ to which I would invite atten- 
tion is one of greater difficulty ; it requires the serious aid of chemistry, 
mineralogy, and the laws of physical forces. The study of the older crystal- 
line and metamorphic rocks has of late years greatly occupied the attention 
of many of those geologists who have examined the chemical and mineralo- 
gical conditions of formations. We are told that heat alone could not have 
produced the results we see ; that water was an essential element in all these 
metamorphic operations; and we find, in the works of Sterry Hunt, Daubree, 
Evan Hopkins, Delesse, Desor, and others, that even a high temperature was 
not necessary to produce these changes. Many of those results which have 
hitherto been considered as the effect of igneous action, are now believed to 
be owing to chemical action. It therefore appears that the time is come 
when it is desirable to investigate this question,— whether the theory of 
central incandescent heat is tenable ? Whether the plastic conditions of the 
earth, to which its oblate spheroidal form has been attributed, be not owing 
to an aqueous rather than to an igneous origin ? W ater is an essential ele- 
ment in every rock, not only mechanically but chemically ; and without 
attempting to revive the doctrine of W erner, it may be questioned whether 
we have not sometimes been disposed to overlook the importance of the 
part it has played in the construction and solidification of our earth.” * 
* Quart. Journal of Geo. Society. May, 1866. Vol. xxii. 
