Now, in opposition to men of this calibre, the unanimity of the greatest practical geologists is a fact of considerable importance. They have devoted year after year to patient investigation. They have had no prejudices to contend with-knowing, even by the logical cast of their minds, that increased knowledge, whatever its form, can never be incompatible with truth-and have spoken of material things; those only that they have beheld with their own senses. Thus Philips,* speaking of aqueous deposits, uses almost the same language which we have before quoted :

"When we find shells and corals," he writes, which, beyond all doubt, must have lived in the sea, deposited in the interior of solid rocks, with all their delicate ornaments of structure uninjured, lying in these rocks as they usually do on the bed of the sea, we are irresistibly compelled to conclude, not only that these exuvia were deposited by the ocean, but that the animals actually lived in, or near, the very spots where their remains are buried, and were there quietly covered up by the ordinary deposits of matter then proceeding. The stratified rocks enclosing these remains were really in succession the bed of the ancient sea; and whenever we find the faithful testimony of marine exuviæ, the conclusion is immediate and unobjectionable, that the ancient bed of the ocean is laid open before In Europe generally, in North America, in India, a large portion of the whole area may thus be proved to have been formerly submerged."

us.

A few pages subsequently-50 - he continues his subject in this strain :-" The magnificent spectacle of continents rising gradually or suddenly from their present waves, is calculated to impress, upon even the least attentive mind, a sentiment of respect for the sublime subjects of geological inquiry.

The following investigation is not intended to accomplish more, than to produce a conviction that a long succession of time elapsed during the construction of the visible crust of the globe.

"In the production of strata, which are composed of fragmented materials of any kind, mechanical forces were exerted; for it is chiefly by the influence of waves and currents that sandy and argillaceous matter is brought to the stratified form. When, therefore, we see even a single sandstone composed of some hundreds of regular layers of sand and mica, and compare this with the deposits from modern rivers or the sea, we shall feel assured, that, in assigning to the accumulation of this rock a considerable space of time, we are proceeding in a just spirit of philosophy.

"If we consider the common case of alternating clays and sandstones, both of which are mechanical deposits from water, but produced under different circumstances, perhaps brought in different directions, the indications of the progress of time become perhaps more clear and satisfactory.

"It is very common to find deposits of limestone, apparently produced by chemical decompositions, lying in frequent alternation with sandstones and clays; and in such a case, by enquiring of the actual system of nature, we receive an answer, that

such changes of the mode of action in a given place imply cessations and renewals of chemical and me- . chanical actions which require time.

"By reviewing in this manner the whole series of strata, amounting locally to some miles in thickness, and considering the accumulation of each bed; the alternation of beds of different kinds; the excitement, duration, suspension, and resuscitation of mechanical and chemical agencies, we shall be strongly impressed with the folly of setting narrow bounds to the time employed in these operations.

"Some stratified rocks are composed of fragments of various kinds, united by a general cement of a different nature. These are called brecciated or conglomerate rocks, according as the fragments are angular or rounded by attrition in water. There is proof in these, that before the production of one stratum, a previously stratified rock had been consolidated; partially broken up; its fragments agitated in water, and then re-deposited. In some cases, conglomerate rocks have been again broken up, and their fragments submitted to the same process of attrition and re-aggregation.

"In some cases, whole rocks are literally composed of zoophytes, so as to resemble a modern coral reef; or of shells of various kinds. The extensive strata of coal are derived from immense accumulations of vegetables, and sometimes no less than fifty consecutively deposited strata of this kind extend over a hundred square miles or more.

"It seems unnecessary to accumulate more evidence to obtain an unanimous verdict from all impartial readers, that the length of time, occupied in the pro

duction of strata, some miles in thickness, which exhibit all this variety of events, was really very great."

M'Culloch, with the boldness, natural to the workings of his mind, but in the same spirit, and on the same induction of evidence, draws out his reasoning to a similar conclusion. "Let us"-is his language "contemplate time as it relates to the Creator, not to ourselves, and we shall no longer be alarmed at the time which the history of the earth demands. Every change which it has undergone has required time: every new deposition of rock has been the work of ages; and the sum of these is the duration which has been reviewed; although this is possibly but a small space compared to that which it has existed as a planetary globe. Every stratum of rock is the work of time; often of far more than we choose to contemplate; while from what we see, we can approximate to that which we know not how to measure. He who can measure and number the strata from first to last, is prepared to solve this question as it relates to the intervals of repose, but those only, not to those of the revolutions; let him ascertain the time required to produce a stratum of a given depth; let him seek it in the increase of colonies of shell fishes, in deposits of peat, and in the earthy deposits of seas and lakes, and he has found a multiplier, not to disclose the truth, but to aid his imagination.

"Who indeed can sum this series? the data are not in our power; yet we can aid conjectures. The great tract of peat near Stirling has demanded two thousand years; for its registry is preserved by the

Roman works below it. It is but a single bed of coal; shall we multiply it by a hundred? We shall not exceed far from it, did we allow two hundred thousand years for the production of the coal series of Newcastle, with all its rocky strata. A Scottish lake does not shoal at the rate of half a foot in a century; and the country presents a vertical depth of far more than three thousand feet in the single series of the oldest sand-stone. No sound geologist will accuse a computer of exceeding, if he allows six hundred thousand years for the production of this series alone. And yet, what are the coal deposits, and what the oldest sand-stone compared to the entire mass of the strata? Let the computer measure the Apennine and the Jura; let him, if he can trust Pallas, measure the successive strata of sixty miles in depth, which he believes himself to have ascertained, and then he may review his computations; while, when he has summed up the whole, his labour is not terminated. But let the reader supply the figures, which it is useless to exhibit, since they cannot be true."*

His argument, in regard to volcanic phenomena, is to the full as rational, and as full of proof; and the conclusion, as to the lapse of time requisite for these operations, in every degree as just. The reasoning of Lyell on this topic is singularly forcible and striking. His work is a perfect mine of facts, which, whether or no we enter into all his deductions, must be read to be fairly appreciated. Extracts, however powerful for a specific purpose, can scarcely give a good idea of the real value of his volumes.

*M'Culloch, system of Geology, vol. i. p. 506. London, 1831.