of a few broken fragments of bones, was able to build up an induction of facts illustrative of the whole form and habits of the animal to which they belonged, might well be pardoned if it tended to magnify the importance of the study. The very novelty of the forms of these lost beings, their unaccountable fate, and the interest of antiquity with which they are invested, render them infinitely more singular to us than the oldest Cheops from a Theban tomb. But is there any thing in their size, structure, or presumed habits, which would seem to have unfitted them for the present system of things? Or, after years of sober consideration, are they still found so strange and anomalous that it should be deemed necessary to construct a pre-adamite world for their reception?

The mastodon does not exceed in size our largest living elephants. The megatherium, prodigiously massive as its skeleton is, may perhaps be rivalled by the unwieldy rhinoceros; and, indeed, animals possessed of a more ponderous frame would have been altogether unsuited for locomotion on our earth as it is now constituted. Then, again, we have existing crocodiles and caymen as large as the plesiosaurus. Our whales of seventy feet in length must be reckoned a match for the dinotherium, which most probably was also an aquatic mammal; and for the huge iguanadon, an equivalent reptile may yet perhaps be found amid our torrid swamps

or savannahs; the pterodactyles or flying quadrupeds have a counterpart in our bats and vampyres. The combinations of structure in these, and in the plesiosaurus and ichthyosaurus are certainly to us curious, because they are new; yet are they more anomalous than that of the existing ornythorynchus? Amid the diversities of form in nature, we cannot properly pronounce any such combinations singular, for they are as much systematic as that of the best defined type of any great group. Neither can we set any limits to the probable combinations of organization-the field for such variation is infinite-nor, with all the grouping and systematizing of naturalists, is there any expectation of filling up and completing the imaginary bounds and limits which have been imposed on the operations of nature. as it has been remarked, only seems to recognize one distinction in her system,-that of the individual and species. Among the extinct animals there are no such diversities from the present as to render the creation of new classes or orders necessary, they are only so far different as to constitute new genera and species of old established classes.

She,

58

SECTION VI.

CHANGE OF TEMPERATURE.

ASSUMING for a moment the truth of a very prevalent opinion, that the temperature of the globe was at one time very high, and that it has gone on progressively cooling to its present rate, we may remark, that even this theory refutes the idea of a long succession of ages being necessary for the formation of the respective strata.

We shall take for example the coal measures,—a mass of alternating strata, from three to five thousand feet thick in its deepest parts, and requiring, according to the liberal allowances of some, not less than a million of years for its formation. Now, the vegetable remains at the bottom of this series are identically the same as those at the top; but had a refrigeration of a million of years taken place in the interval, the last lepidodendron and fern should have had a totally different character from the first. The same remark applies to beds of molluscous animals.

But, indeed, we can never consider the common theories of central heat as compatible with the. existence of plants or animals in a considerable portion of the globe, at any period of its past or present existence. Thus, all will allow that our present tropical temperature is due to the sun's influence alone, and the average of this heat for several months is upwards of one hundred degrees of Fahrenheit. Now, to this average heat, which must have been produced ever since the sun shone upon the earth, add fifty or sixty degrees of central heat, and we have a climate that might boil plants and animals, but would never permit them to exist.* And yet we have the carboniferous coal fields of India with the same fossils, and coeval, it is said, with the same systems of Britain! The temperature of the former and present surface of the earth, different as it seems to have been, must, we suspect, be explained on other data than theories of central heat, and none seem more fitted for this purpose than the relative change of position of large portions of land and sea, as illustrated in so ingenious a manner by Mr Lyell.+

* The mean tropical heat is calculated at 81 degrees.

At Cawnpore, E. I. in April and May, 1789, the mean heat was 127 degrees,-maximum 144 degrees.

At Allahabad, E. I. the heat is often 109 degrees in the shade.

In Georgia, maximum of heat 105 degrees.

A heat of 109 degrees proved fatal to ten thousand persons in

China.

+ Note VI.

Allowing the probability of this latter theory, the following considerations seem accordant to facts,—

The change was sudden and abrupt. In Europe we have no traces of intermediate vegetation between the system of extinct plants and existing species. We have animals of tropical temperatures supplanted by our present races, and some of the former, as the Siberian elephant, suddenly enveloped in clay, and frozen over so as to be completely preserved.

The change was extensive, because the coincidence of the same plants, as in the carboniferous system, and the same animals, as in fossil beds and diluvium, extending over many regions of the globe, exhibiting one era of existence, all indicate a similarity of climate. This temperature, though more elevated and uniform than that of our temperate and frigid zones, may not, however, have been even equal to our present tropical. We cannot determine, in fact, how slight or how great an elevation of temperature may have been necessary for the growth of fossil plants, or the existence of fossil animals. Thus, the Siberian elephant was clothed with long hair, indicative of a temperature not extremely warm, probably analogous to many mountainous regions in Asia, where hairy elephants were seen by Bishop Heber.