4 Notice of the Wonders of Geology. 
igneous rocks must supply their materials; at least their materials 
must come from below, and may be furnished also in part by chem- 
ical effluxes from the interior of the globe, a hint that may serve to 
explain whence the materials of the early caleareous and magnesian 
rocks are derived. In our continued ascent, we soon encounter the 
strata containing the oldest fossils, the marine animals that occu- 
pied the earliest seas, relics entombed in the transition rocks of 
Werner, the Cambrian and Silurian of Sedgwick and Murchison. 
From those profound depths, where animal and perhaps vegetable 
life approximates to the granite epoch, we follow its continued de- — 
velopments through the immense piles of natural masonry that 
form the stratified rocks, replete also with the remains of the living 
beings of succeeding ages, but changing their character continu- 
ally, as we ascend, until, in ages very remote from those which 
cherished the earliest forms of life, we discover the beginning of 
terrestrial existence, of the animals that lived on dry land; and thus 
at length we arrive at the era of the human race, the last in the order 
of the creation. In this mode of treating the subject, there are few 
anticipations, and the chronology is perfectly preserved. 'The 
action of water will, of course, be studied through the whole se- 
ries; it is necessary to have regard to water in solving even the 
phenomena of fire, and it is of course admitted by all, as the 
great agent in stratification. We may finish by considering water 
in its widely ranging effects, as seen at the present time. 'The 
phenomena of vallies, rivers, and fountains, and of all that ap- 
pears on the surface, may be studied in the conclusion of the se- 
ries, with all the lights that have been afforded by the preceding 
investigations ; nor can we forget the proofs of wise and benevo- 
lent design which are apparent through all the formations, and 
that shine forth so remarkably in the various affections of the sure 
face, the prepared and arranged theatre of human action. 
No particular order is however absolutely essential to geology ; 
for begin where we may, we can always revert; we can thread 
our way, back and forward, as occasion may require, until the laby- 
rinth, at first dark, devious and appalling, becomes illuminated, 
and we walk securely in the light of science, guided by the clue 
of strict induction, which leads us, with unerring steps, through 
all the phenomena. 
~ Dr d has preserved a strict unity of plan in the treat- 
ment of his subject ; each division is made perfectly clear and in- 
# 
“ 
