Geological Society of London. 115 
ral climate, animal and vegetable life has been sustained, This ap-_ 
pears to have been accomplished without violation of those laws now 
governing the organic creation, by which limits are assigned to the 
variability of species. There are no grounds for assuming that spe- 
cies had greater powers of accommodating themselves to new cir- 
cumstances in ancient periods than now. The succession of living 
beings was continued by the introduction into the earth from time to 
time of new plants and animals. ‘That each assemblage of new spe- 
cies was admirably adapted for successive states of the globe, may: 
be confidently inferred from the fact of the myriads of fossil remains 
preserved in strata of all ages. Had it been otherwise, had they 
been less fitted for each new condition of things as it arose, they 
would not have increased and multiplied and endured for indefinite 
periods of time. 
Astronomy had been unable to establish the plurality of habitable 
worlds throughout space, however favorite a subject of conjecture 
and speculation ; but geology, although it cannot prove that other 
planets are peopled with appropriate races of living beings, has de- 
monstrated the truth of conclusions scarcely less wonderful, the ex- 
istence on our own planet of many habitable surfaces, or worlds as 
_ they have been called, each distinct in time, and peopled with its 
peculiar races of aquatic and terrestrial beings. 
Thus as we increase our knowledge of the inexhaustible variety 
displayed in living nature, and admire the infinite wisdom and power 
which it displays, our admiration is multiplied by the reflection that 
it is only the last of a great series of pre-existing creations of which 
we cannot estimate the number or limit in past time. 
All geologists will agree with Dr. Buckland, that the most per- 
fect unity of plan can be traced in the fossil world throughout all the 
modifications which it has undergone, and that we can carry back 
our researches distinctly to times antecedent to the existence of man. 
We can prove that man had a beginning, and that all the species 
now contemporary with man, and many others which preceded, had 
also a beginning ; consequently the present state of the organic world 
has not gone on from all eternity as some philosophers had main- 
tained. 
But when neste the truth of these propositions, I am pre- 
pared to contest another doctrine which the Professor advocates, 
namely, that by the aid of geological monuments we can trace back 
the history of our terraqueous system to times anterior to the first 
