Geology teaches the same thing.—Of the various formations that compose the earth’s trust, to the ascertained extent of ten miles, suppose we select two,—the Old Red Sandstone and the Chalk formations. Laborious and scientific men have been at the pains to calculate the gradual increase of some of these _now proceeding deposits_,—such as the Deltas, in course of formation at the mouth of the Nile, and at the gorges of the Ganges; and they find that the progress of the depth of increase is exceedingly small,—probably not more than a foot in many years. Mr. Maculloch, a name standing very high for accurate investigation, states, from his own observation, that a particular Scottish lake does not form its deposit at the bottom, and hence raise its level, at the rate of more than half-a-foot in a century; and he observes, that the country surrounding that lake presents a vertical depth of far more than 3,000 feet, in the single series of the Old Red Sandstone formation; and no sound geologist, he hence concludes, will, therefore, accuse the computer of exceeding, if, upon the same ratio as the contiguous lake, he allows 600,000 years for the production of this series of rock alone. A last instance which may here be adduced, of the apparent length of time required for the construction of a particular rock, offers itself in the Chalk formation. The enormous masses of this rock, presenting their tall white precipices in such simple grandeur to our view, might well excite our astonishment at the periods which would seem needful for their collection and deposition, even if they were mere _inorganic_ concretions of calcareous matter. But what shall we say when the investigations of the microscope have lately revealed to us that these mountains of chalk, instead of being formed of mere inert matter, are, on the contrary, mighty congeries of decayed animal life,—the white apparent particles, of which the chalk masses are composed, being each grain a well-defined organized being, in form still so perfect, their shells so entire, and all their characteristics so discoverable, as to cause no doubt to naturalists as to the species in the animal economy to which they belonged. How justly does Sir Charles Lyell, who in his “Elements” records at length this surprising discovery, exclaim,— “The dust we tread upon was once alive!” “Look at the lofty precipices which lay naked a slight section of the Chalk at the Culvers, or the Needles in the Isle of Wight, or the still loftier Shakspeare Cliff at Dover, and let the mind form a conception, if it can, of the countless generations of these minutest of living creatures it must have required to build up, from their decayed bodies and their shelly exuviæ, layer on layer, those towering masses thus brought to our view. Who shall dare to compute the time for this entire elaboration? The contemplation almost advances us a step towards forming a conception of infinitude.”[124]