The last year of this decade is drawing to a close. At this ending of the season, the mind naturally turns back to a review of the past; and, in turning back, the student of science is drawn to contemplate the long periods which geology and astronomy have revealed to our knowledge. The thong1lt flits o\er the time of man's history, as forming hut a step to the vast vista which stretches beyond. Reading the record of the rocks, we find that, before the human mce made its appearance in the universe, our globe Was inhabited hy mammoths, megatheriums, mylodons, mastodons, and other llUge quadrupeds, fur larger than any that now roam upon its surface. For tllOusands of years these animals multiplied, lived and died, till at last, in the fullness of their time, they hecame extinct. If we follow back the conrse of geological history, to the first coming of the mammalia, we find the earth swarming with lizards and othcr lower forms of nnimated heing. Beyond the lizards again there was an immense period in which the sea W:IS filled with fishes, but during which there was no animal upon the land. Long before thc higher orders of fishes were created there were hosts of the lower forms of marine life, stnr fishes, trilobites nnd polypi, existing in such immense nnmbers and through such periods that strata of the older rocks, of unmeasured 408 thickness, arc almost wholly composed o; their remains. And thi* is as far as our positive knowledge extends ; for whether, at the time of the formation of the oldest plutonic rocks, there were animals whose remains have been since entirely destroyed, we have no means of determining. There are, however, indications which have led to the general belief, that there was a time when the earth was whirling upon its axis, and sweeping in its long journey around the sun, through year after year, and century after century, without a living thing upon its surface. It is probable that the earth was then so hot that the matter now constituting the waters was all diffused in vapor, funning a cloud so deep and dense that no ray of sun or star could pierce through it. “ And the earth was without form, and void and darkness was upon the face of the deep." Where the positive facts of geological science fade away into dim conjecture, we enter upon the still more sublime revelations of astronomy. The observations of the nebula? by Sir William Herschel and his successors render it probable that the matter of the solar system did once exist in minute self-luminous particles, like a vast firey cloud, which was sailing swiftly along in its immense orbit, while its matter was being slowly condensed into the globes which we call the sun and his attendant planets. And here, at last, in its backward journey through the abyss of the past, the mind loses all guidance of reason or observation. In what condition matter existed before the formation of the nebula;, we have no grounds even for conjecturing. We only know that duration must have been ; for, it is a self-evMent truth, that time could have had no beginning, as it can have no end.