THE LAPSE OF TIME.

THE divergence of opinion between scientific and unscientific persons is scarcely anywhere more conspicuous than in their measurements of the age of the world we live in. A popular impression still prevails that the old beldame earth, as Hotspur calls it, is about six thousand years of age. A little margin is sometimes allowed. By an exercise of heroic liberality a period of ten or twelve thousand years is occasionally conceded for the earth's existence. Any chronology discontented with these ample limits comes within the domain of rash and dangerous speculation. Some, indeed, who would fain conciliate all parties, are willing to extend the bounds on certain conditions. They will grant a large extra slice of time, provided that during that period the earth was a shapeless uninhabited lump, or if inhabited, not inhabited by men. 'Come, now,' says the cheap-jack, I'll tell you what I'll do with you; I'll throw you in another five thousand years; fifteen thousand years! and take the lot. What! not do? I'll make it twenty thousand.

Now, I'll tell you what I'll do with you: I'll make it five-and-twenty thousand years, and if that won't satisfy you, you aren't worth arguing with.'

What scientific men think of the cheap-jack's offer it is the object of this essay to consider.

The problem upon which many thoughts and speculations of science are for the moment converging is the origin of life. There are some who believe that under certain chemical conditions living creatures are continually coming into existence, ungenerated by any living parent, born as it were without birth, acquiring an animated existence, with powers of motion, feeding, and reproduction, from substances previously wanting in one or all of these capacities; such creatures, in short, as, if asked for their parentage, could but answer, each for itself, my father was an atom, and my mother a molecule. It should be remembered that the little animals supposed to arise in the manner described first become visible, if at all, as the tiniest objects that microscopes can detect. But whether there is or is not in these days a continual coming into existence of these infinitesimal pigmies, they are just such productions as the Theory of Development would suppose to have arisen originally, constituting the first outburst of life upon the globe, ancestral to the noblest forms of animated nature now extant, progenitors in an unbroken line of man himself. As a rule, among living things we find that offspring bear a tolerably exact resemblance to their parents. The lower the organism the less easy is it to distinguish specimens

of one generation from those of another; and even in the most highly organized creatures the points of resemblance generally far outweigh the points of difference between the parents and their children. In short, under ordinary circumstances, not one generation only, but a hundred, may pass away without registering any perceptible alteration in the character of a species. A hundred generations of mankind would require a period of about three thousand years. A hundred generations of less important creatures might not perhaps require even as large a number of hours. But between the two extremes the necessary periods would bear a kind of ratio to the perfection of the organism. Variations might now and then follow one another in quick succession, and then a pause come of a thousand generations or so before any further changes in the character of a species.

Such are the conditions under which Mr. Darwin and his followers believe it possible for the whole sequence of changes to have been effected, which have ended in peopling the whole earth with a countless variety of the most diverse forms of life. Many persons are horrified at the notion of linking together a man and a monkey even by the most distant ties of consanguinity; what will they say to a genealogy which begins with an almost invisible speck and ends with a Patagonian giant—a genealogy which asserts that, through the slow process of minute changes oceurring for the most part at rare intervals, our fair humanity has been developed or evolved out of creatures

which no unaided human eye could distinguish from the dust on which we carelessly trample. To some ears such a theory must sound wild and preposterous beyond all the boundaries of sane and rational thinking. And, in truth, no censure could be too severe, no ridicule too keen for so extravagant a piece of folly as this theory must be, if the old and still prevailing notions about the age of the world have any foundation in fact. It only begins to be reasonable, if we can afford to stretch our notions of history from the narrow margin of six thousand to the broader field of six hundred thousand years, with an indefinite past in the background.

This vast lapse of time, as commensurate with the existence of the inhabited globe, is essential to the Theory of Development. It must be established, as it has been, by independent evidence of its own, before it can give to that theory its absolutely necessary support. But the Theory of Development in its turn helps the mind to believe and realize this enormous lapse of time, with its seemingly never-ending march and flow, rank upon rank, wave upon wave, by finding work and employment for all its almost measureless duration. It explains, as it were, why the drama of life still goes on, why the play was not long ago played out, and the curtain let fall upon all the busy multitudinous actors.

Time of itself does nothing; but nothing can be done without time. It is not a personal agent, but a necessary condition. We cannot even think, much less rea

son, of things as occurring out of time and independently of it, any more than we can think or reason of matter as existing independent of space. Every occurrence takes time and yet we may not leap from this fact to the conclusion that a countless multitude of occurrences will require a vast duration of time. Professor Tyndal, in his Lecture on the Scientific Use of the Imagination, refers to waves of light less than 5000 of an inch in length. How many do you suppose of such waves would be required to compass a mile? How many to accomplish the 185,000 miles which light travels in a second? Each undulation is a separate occurrence, so that we have millions of millions of occurrences following one upon another in a second of time. In studying, therefore, the complete fabric of the globe, or even of the whole material universe as far as it comes within our ken, the problem for solution is not whether these great results could or could not have been brought to pass in an indefinitely short space of time, in the twinkling of an eye, as one might say, but whether the space of time employed in their production has actually and in fact been indefinitely short or indefinitely long. We ought also to bear in mind that the terms we use when we speak of long and short, are relative not absoluterelative to the duration of our own lives, or to some other arbitrary standard which we are pleased to set up for purposes of comparison. Thus a year is long compared with a minute, but short compared with a millennium; a thousand years would be an enormous length

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