taneous generation and the only conditions under which we can imagine spontaneous generation to have occurred. There is some difference, we submit, between a small flask with a few ounces of hay infusion, to which no air has been admitted, which has not been submitted to a number of life-destroying processes, and a young planet teeming with material vitality, still hot with its primeval fires, still palpitating from the throes which (during countless ages) had preceded and accompanied its birth. No experiment or observation man has ever made or can ever make, can suffice to show that the spontaneous generation of living forms then was either possible or impossible. But men may continue, if it gives them any comfort, to believe that just then the uniform action of law was interrupted, that just at that stage the mechanism of the universe was found to be imperfect.

But while in this sense and to this degree the law of biological evolution differs from the law of universal attraction, the work of Darwin must yet be regarded as akin to that of Newton, in that it extends indefinitely our conceptions of the range of natural laws. As Newton showed men all the millions of families of worlds throughout the universe moving in accordance with the law of attraction, so Darwin has shown us all the myriads of races which have inhabited the earth brought into due relation to their surroundings by the operation of the law of evolution. And as the law of gravity was but a wider law, including such laws as Copernicus and Kepler had recognised, which in turn severally included many minor laws, so it should be noticed that the law of biological evolution includes all those minor laws of development which men had recognised for ages without entertaining the unreasonable thought that such laws necessarily implied the non-existence of a lawgiver.

To those alike who are pained and to those who rejoice at what they regard as the irreligious tendency of the doctrine of biological evolution, the same answer may be made: it is only when we try to create arbitrary limits of space or

of time, and to set these as bounds to the operation of the laws of Nature, that any such tendency can be imagined. Those who have admitted the growth of a tree, a forest, or a flora, of an animal, a race, or a fauna, according to natural laws, have to acknowledge nothing new in kind, however different it may be in degree, in admitting that there is development on the larger scale as well as on the smaller, not even though they should have to admit that such development takes place throughout all space and all time. The difficulty in dealing with one thought is not greater than that which oppresses us in considering the other; both difficulties are overwhelming, both infinite. If we could evade the conception of the infinite in space or in time, we might be content to imagine limits to the operation of law. But we can neither evade the conception nor grasp it. As Pasteur has well said, quite recently—' When the question is asked, "What is there beyond the starry vault?" it is useless to answer, " Beyond lies unlimited space." When we ask what lies beyond the far-off time when what we see around us began to be, and what lies beyond the remote future when it will cease to exist, of what use the answer, "Beyond lie eternities of past and coming time"? Nobody understands these words. He who proclaims the existence of an Infinite --and nobody can evade it—asserts more of the supernatural in that affirmation than exists in all the miracles of all the religions; for the notion of the Infinite has the twofold character of being irresistible and incomprehensible. When this notion seizes on the mind, there is nothing left but to bend the knee. In that anxious moment all the springs of intellectual life threaten to snap, and one feels near being seized by the sublime madness of Pascal. Everywhere I see the inevitable expression of the Infinite in the world. By it the supernatural is seen in the depths of every heart.'

It is as thus viewed that the laws of development brought before us during the last quarter of a century—not as novelties, for in conception they are of vast antiquity, but new in the sense that now for the first time they are presented as

proven-are so solemn and impressive when rightly understood. As the discoveries of astronomy were first steps towards infinite space, steps carrying us far enough upon the road to show that of necessity it must be infinite, as the study of the movements of the heavenly bodies tells us unmistakably of infinite time, so the recognition of development tells us that, as we might have anticipated, the domain of law is limitless alike in space and in time. With the angel in Richter's Dream, Science, in the doctrine of Everlasting Evolution, proclaims the solemn truth,-End is there none to the universe of God; lo, also, there is no Beginning.'

THE VISTAS OF THE PAST.1

MANY of those who follow with interest the teaching of science, but have not leisure to study carefully the methods and principles on which those teachings depend, are inquiring what new views are these according to which the moon was born of the earth many millions of years ago, and has been retreating ever since from the parent orb; how those views are related to the nebular hypothesis of Laplace; and what bearing they may have on astronomical and geological estimates of past eras in the earth's history. An eloquent lecture by the Astronomer Royal for Ireland has done much to increase the interest with which these questions are viewed; indeed, it may be doubted whether many who are now inquiring about these matters had heard of them at all before Dr. Ball brought them before the attention of the audiences to whom his lecture has been addressed.

I propose to sketch the ideas resulting from the researches of Mr. George Darwin, noting how they are related to former views respecting the development of the solar system, and how they bear on certain other astronomical and geological theories. At the outset I may remark that I cannot altogether agree with the opinions expressed by Dr. Ball, and to some degree by Mr. Darwin, respecting the manner of the moon's birth; but as to the general theory to

1 This essay should be read in connection with that which follows. It will be found that they are in a sense supplemental to each other, portions which are fully treated in one being summarised in the other, and vice versa.

which Mr. Darwin's researches have led there seems very little room for doubt or question.

In carrying back our thoughts to the past of the earth, our most trustworthy guide (though we must be careful in following even this guide) is evidence found in the study of processes actually taking place at the present time. For instance, we find that the earth is slowly cooling. We can, therefore, go back to a time when she was much hotter than she is at present; and though we may not be able to assume confidently that her temperature was ever so great as to cause every particle of her substance to be vaporised, we may infer even that, if other features actually existent seem readily explicable on such an assumption. Again, we find that the earth gathers in every year hundreds of millions of meteoric masses of greater or less weight, down to bodies weighing only a few grains; and we know from the orbits followed by the greater number of these that they belong to systems travelling around the sun on paths of such a nature as to forbid us to believe that they were originally expelled from the earth. Seeing, then, that the earth is gathering in materials from without, though now at a very slow rate, and seeing further that this process is of necessity one which takes place more and more slowly as time proceeds, we are justified in looking back to a time when it progressed far more quickly than at present, in considering that over the whole intervening period-many millions of years-it has been at work, and finally in inferring that no unimportant part of the earth's present mass has been derived in this way from meteoric aggregation.

Now, among other processes of change that are taking place in the earth and her dependent or associate orb, the moon, are two others, discovered in comparatively recent times, though not quite so recently as some might infer from Dr. Ball's account. About a quarter of a century ago Professor Adams, co-discoverer with Leverrier of the distant Neptune, announced that he had discovered an error in Laplace's discussion of the so-called acceleration of the