Phillips — Geological Address. 177 
and systematic diversity as the remains of plants and animals. By 
appeals to these innumerable witnesses, conclusions of much im- 
portance are maintained, touching the greater warmth of the Car- 
boniferous land, and the colder climate of the later Canozoic seas. 
By the same testimony, it appears that over every part of the earth’s 
surface, in every class of organic life, the whole series of created 
forms has been changed many times. 
Have we measured these changes of climate, and assigned their 
true physical causes? Have we determined the law of the successive 
variations of life, and declared the physiological principles on which 
the differences depend? No! the variations of climate must be 
further investigated, the limits of specific diversity more surely de- 
fined, before we can give clear answers to these critical questions. 
Late researches, partly archeological and partly geological, both in 
England and France, have been held to prove the contemporaneity 
of Man and the Mammoth in the northern zones of the world. Have 
we, then, been too confident in our belief that the human period was 
long posterior to, and strongly marked off from, that of the Cavern 
Bear and the woolly Rhinoceros? Did the races of Hyzna and 
Hippopotamus remain inhabitants of Europe till a comparatively 
modern epoch, or was Man in possession of the earth in times far 
earlier than history and tradition allow ? 
The prevalent opinion seems to be, that, as variations of the forms 
of life are extremely slow in existing nature, for every case of con- 
siderable change in the predominant types of ancient plants and 
animals, very long intervals of time must be allowed to have elapsed. 
If in some thousands of years of human experience no very material 
change has happened in our wild plants or wild animals, or in culti- - 
vated grains, or domestic birds and quadrupeds, it is evident that no 
considerable changes of this kind can arise from such causes as are 
now in action without the aid of periods of time not contemplated in 
our chronology. Estimated in this way, the antiquity of the earth 
grows to be inconceivable—not to be counted by centuries, or 
myriads of years—not to be really compassed by the understanding 
cf men, whose individual age is less than a century, and whose his- 
tories and traditions, however freely rendered, fall short of a hundred 
centuries. The whole human period, as we have been accustomed 
to view it, is but a unit in the vast sum of elapsed time: yet in all 
those innumerable ages the same forces were seated in the same par- 
ticles of matter ; the same laws of combination prevailed in inorganic 
and in living bodies; the same general influences resided on the 
surfaces or governed the masses of the planets, in their ever-changing 
paths round the sun. 
All natural effects are performed in time, and when the agency is 
uniform, are in proportion to the time. And though the agency be 
not uniform, if the law of its variation be known, the time consumed 
in producing a given effect can be determined by calculation. Geo- 
logical phenomena of every order can be expressed in terms of 
magnitude, as the uplifting of mountains, the deposition of strata, the 
numerical changes of the forms of life. The time required to produce 
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