[Transcriber Note: Errata Corrections HAVE BEEN applied to text!]
I
THE CHAIN OF LIFE TRACED BACKWARD IN
GEOLOGICAL TIME
I
IN infancy we have little conception of the perspective of time. To us the objects around us and even our seniors in age seem to have always been, and to have had no origin or childhood. It is only as we advance in knowledge and experience that we learn to recognise distinctions of age in beings older than ourselves. In thinking of this, it seems at first sight an anomaly, or at least contrary to analogy, that the oldest literature and philosophy deal so much with doctrines as to the origins of things. In this respect primitive men do not seem to have resembled children; and the fact that our own sacred records begin with answers to such questions, and that these appear in the oldest literary remains of so many ancient nations, and even in the folk-lore of barbarous tribes, might be used as an additional argument in favour of an early Divine revelation on such subjects, as a means of awakening primitive men to the comprehension of their own place in the universe.
However this may be, it is certain that modern science at first took a different stand.
The constancy of the motions of the heavenly bodies, our great time-keepers, and of the changes on the earth depending upon them, and the resolution of apparent perturbations into cycles of greater or less length, impressed astronomers and physicists with the permanence of the arrangements of the heavens and their eternal circling round without any change. In like manner, on the rise of geology, the succession of changes recorded in the earth seemed interminable, and Hutton could say that in the geological chronology he could see "no vestige of a beginning, no prospect of an end."
But the progress of investigation has changed all this, and has brought physical and natural science back to a position nearer to that of the old cosmogonies. Physical astronomy has shown that the constant emission of heat and light from the sun and other stars must have had a beginning, and is hurrying on toward an end, that the earth and its satellite the moon are receding from each other, and that even the spinning of our globe on its axis is diminishing in rapidity. In summing up these and other changes, Lord Kelvin says: "To hold the doctrine of the eternity of the universe would be to maintain a stupendous miracle, and one contrary to the fundamental laws of matter and force."
So, on our earth itself, we can now assign to their relative ages those great mountain chains which have been emblems of eternity. We can transfer ourselves in imagination back to a time when man and his companion animals of to-day did not exist, when our continents and seas had not assumed their present forms, and even when the earth was an incandescent mass with all its volatile materials suspended in its atmosphere. It is true that in all the changes which our earth has undergone the same properties of matter and the same natural laws have prevailed; but the interactions of these properties and laws have been tending to continuous changes in definite directions, and not infrequently to accumulations of tension leading to paroxysmal vicissitudes.
If all this is true of the earth itself, it is especially applicable to its living inhabitants. Successive dynasties of animals and plants have occupied the earth in the course of geological time; and as we go back in the record of the rocks, first man himself and, in succession, all the higher animals disappear, until at length in the oldest fossiliferous beds only a portion of the more humble inhabitants of the sea can be found. In the time of the formation of the oldest of these rocks, or perhaps somewhat earlier, must have been the first beginning of life on our planet.