President's Address. 
113 
degredation of a former world the present strata have ori- 
ginated. The second principle assumed in the Huttonian 
theory is that the materials which are collected at the 
bottom of the ocean are at great depths exposed to the action 
of an intense heat, under very strong pressure, by which 
they are fused and consolidated, so as to be capable of 
forming new strata. The theory of Hutton was adopted by 
Playfair, Hall, and others, in opposition to the Wernerian 
views, at that time also vigorously upheld and taught by 
Professor Jameson, formerly a pupil of the celebrated philo- 
sopher of Freiberg; and, indeed, the intellectual contest 
carried on between the supporters of the rival systems is a 
matter of history. In the Huttonian theory the old hypo- 
thesis of a central heat became allied to the science of 
geology, and w^as for a time a favourite theory with many 
of our best writers, and used with great freedom, if not 
license, by some practical and professional geologists. The 
chief facts on which the speculation is based are the follow^- 
ing:— 
\st, The existence of volcanoes. 
2(i, Earthquake phenomena. 
3c?, Kocks of igneous formation. 
^th, Thermal springs. 
bth^ The increase of temperature in mines in proportion 
to* their depth, and also in water in relation to the depth of 
the strata from which it flows ; and, 
The configuration of the earth. 
I. The Existence of Volcanoes. — The argument derived 
from volcanoes in favour of a central heat rests mainly upon 
the fact of the universal spread of volcanic activity over the 
whole surface of the globe. They exist amongst the snows 
of the Arctic regions and amongst the islands of the Southern 
Ocean ; in the south of Europe ; in Central Asia, South 
America, the West Indies, and over the whole islands of 
the Indian Sea. Hence it is inferred that this general dis- 
tribution of volcanic action is more likely to depend upon 
one common cause, than to have its origin in a number of 
local and detached causes. It is evident, however, that the 
