Thus concludes the wondrous section of the earth's history which is told by geology. It takes up our globe at an early stage in the formation of its crust--conducts it through what we have every reason to believe were vast spaces of time, in the course of which many superficial changes took place, and vegetable and animal life was gradually evolved--and drops it just at the point when man was apparently about to enter on the scene. The compilation of such a history, from materials of so extraordinary a character, and the powerful nature of the evidence which these materials afford, are calculated to excite our admiration, and the result must be allowed to exalt the dignity of science as a product of man's industry and his reason. It is now to be remarked that there is nothing in the whole series of operations displayed in inorganic geology which may not be accounted for by the agency of the ordinary forces of Nature. Those movements of subterranean force which thrust up mountain ranges and upheaved continents stand in inextricable connection, on the one hand, with the volcanoes which are yet belching forth lavas and shaking large tracts of ground, as, on the other, with the primitive incandescent state of the earth. Those forces which disintegrated the early rocks, of which detritus formed new beds at the bottom of the sea, are still seen at work to the same effect. To bring these truths the more nearly before us, it is possible to make a substance resembling basalt in a furnace; limestone and sandstone have both been formed from suitable materials in appropriate receptacles; the phenomena of cleavage have, with the aid of electricity, been simulated on a small scale, and by the same agent crystals are formed. In short, the remark which was made regarding the indifference of the cosmical laws to the scale on which they operated is to be repeated regarding the geological. A common furnace will sometimes exemplify the operation of forces which have produced the Giant's Causeway; and in a sloping ploughed field after rain we may often observe, at the lower end of a furrow, a handful of washed and neatly deposited mud or sand, capable of serving as an illustration of the way in which Nature has produced the deltas of the Nile and Ganges. In the ripple-marks on sandy beaches of the present day we see Nature's exact repetition of the operations by which she impressed similar features on the sandstones of the carboniferous era. Even such marks as wind-slanted rain would in our day produce on tide-deserted sands have been read upon tablets of the ancient strata.