23. And as the infinite extent which we necessarily ascribe to space, allows us to find room, without any mental difficulty, for the vast distances which astronomy reveals, and even leaves us rather embarrassed with the infinite extent which lies beyond our farthest explorations; so the infinite duration which we, in like manner, necessarily ascribe to past time, makes it easy for us, so far as our powers of intellect are concerned, to go millions of millions of years backwards, in order to trace the beginning of the earth's existence,--the first step of terrestrial creation. It is as easy for the mind of man to reason respecting a system which is billions or trillions of miles in extent, and has endured through the like number of years, or centuries, as it is to reason about a system (the earth, for instance,) which is forty million feet in extent, and has endured for a hundred thousand million of seconds, that is, a few thousand years. 24. This statement is amply sufficient for the argument which we have to found upon it; but before I proceed to do that, I will give another view which has recently been adopted by some geologists, of the mode in which the successive periods of creation, which geological research discloses to us, have passed into one another. According to this new view, we find no sufficient reason to believe that the history of the earth, as read by us in the organic and mechanical phenomena of its superficial parts, has consisted of such an alternation of periods of violence and of repose, as we have just attempted to describe. According to these theorists, strata have succeeded strata, one group of animals and plants has followed another, through a season of uniform change; with no greater paroxysm or catastrophe, it may be, than has occurred during the time that man has been an observer of the earth. It may be asked, how is this consistent with the phenomena which we have described;--with the vast masses of ruin, which mark the end of one period and the beginning of another, as is the case in passing from the coal measures of England to the superincumbent beds;--with the highly-inclined strata of the central masses, and the level beds of the upper formations which have been described as marking the mountain ranges of Europe? To these questions, a reply is furnished, we are told, by a more extensive and careful examination of the strata. It may be, that in certain localities, in certain districts, the transition, from the mountain limestone and the coal, to the superjacent sandstones and oolites, is abrupt and seemingly violent; marked by _unconformable_ positions of the upper upon the lower strata, by beds of conglomerate, by the absence of organic remains in certain of these beds. But if we follow these very strata into other parts of the world, or even into other parts of this island, we find that this abruptness and incongruity between the lower and the higher strata disappears. Between the mountain-limestone and the