Another important result of these investigations was to prove experimentally that matter is inert, and that it exercises no initiative of its own; that it is moved only by external agencies; and that, in physics, action and reaction are always exactly equal and opposite, from which it follows that all material things are under the reign of law. This cannot be taken as a proof that mind is absent from dead matter, for it is possible to conceive mind as present, but unable to manifest itself to us. But the experiments destroyed the supposed basis of fact on which Pantheism had formerly been built, and reduced it to a purely metaphysical speculation.

If, however, science showed that the original basis of Pantheism was erroneous, it now furnished new evidence, which seemed to place that philosophy on a firmer foundation than

ever.

Up to the middle of last century, it seemed probable that the Universe might be eternal. Matter and energy were known to be indestructible, and it followed that the amount of each in the universe must be fixed and unalterable. Also, the mathematicians, Lagrange, Poisson, and Lapiace, were supposed to have demonstrated that the Solar System was truly a perpetual motion. Even in the earth itself, the celebrated geologist, Dr. James Hutton, sought, as he said, in vain, for any "vestige of a beginning or prospect of an end." So far as could then be seen, the world might go on for ever as it is now, an endless succession of similar years and of nearly similar plants and animals. It was not even necessary to suppose, with Democritus, that the Universe was the result of a fortuitous concourse of atoms, for there was no beginning. The Universe had always been here, and here it would remain. Life, they thought, had always been on the earth, and where life was there also was mind. And just as one form of matter, or one form of energy, passed into another, so life kept renewing itself-constant decay and death with constant rejuvenescence. If matter was indestructible, so, also, was mind. All was eternal. made to go on for ever. No controller was necessary. The Universe and its Maker were one.

All was

Thus, the conclusions of science seemed to prove that mind pervades all matter; and this belief was more acceptable to our reason than the opposite one, that mind can exist out side of matter, for of the latter we have no experience. Thus, a pantheistic, or monistic, view of the Universe became prevalent, especially in Germany. As the study of palæontology advanced, the succession of life on the earth became a difficulty, and Darwin's theory of organic develop

ment, by means of natural selection, was hailed with delight as the explanation so long hoped for. But, in truth, the pantheistic argument was completely destroyed by the establishment of the theory of evolution, which showed that the Universe was not eternal, and that progress, not repetition. was the law under which it existed.

The change thus brought about was sudden and perplexing, and some very able men could not see their way clearly. So they called themselves Agnostics, thinking that no wellestablished beliefs on theological questions were possible to the impartial investigator. If this had been correct, it would have been a fatal objection to the claim, which was at the same time being made, that science should be included in general education. Fortunately, broader and more sensible views have prevailed, and it is no longer considered that a scientific man must necessarily be an Agnostic.

AN OUTLINE OF EVOLUTION.

Let me now give you an outline of this theory, which wrought such a momentous change.

The idea of evolution originated with the Greeks. but only as a speculation, which led to nothing; and its scientific his tory may be said to commence in the early part of the last century, when the practically new theory of the origin of species by gradual development was proposed by Lamarck. This theory was at first discredited for lack of evidence, but it was developed and demonstrated by C. Darwin in the middle of the century. About the same time, it was pointed out by Lord Kelvin that not only was the sun cooling, but that all kinds of energy, when converted into heat, lost a portion by radiation into space, and that this process must go on until the whole universe was of a uniform temperature. So that, although the amount of energy in the Universe remains unalterable, it will, by re-distribution, be brought into the potential state, and thus, when every possible action is counterbalanced by other actions, energy will practically disappear.

From this theory of "dissipation of energy," it follows that, as the earth is cooling, life cannot go on for ever;. and also that at some former time the earth must have been too

hot for the existence of protoplasm. Consequently, life can only have a limited existence on the earth. It must have had a beginning, and must come to an end.

But the inference extended further. Not only living beings, but even the whole Solar System, must have had a beginning, not indefinitely remote; because most of its mem

bers still contain a large amount of their original heat. And if the Solar System had a beginning, so, also, must each star in the heavens have had a beginning; for the very fact that we can see them is a proof that they are radiating out energy. And, it was asked, why should not the whole Universe, visible and invisible, have had a common origin and a common beginning in time? This had been the opinion of Immanuel Kant in the middle of the eighteenth century, and, although modern astronomy has not altogether confirmed his speculations, it has proposed a hypothesis which is not very dissimilar. This is the "Meteoritic Hypothesis," and is chiefly the work of Sir Norman Lockyer and Professor G. H. Darwin. I will give you a short sketch of the views held by the former.*

INORGANIC EVOLUTION.

The close connection between the orbits of comets and those of meteoritic streams has led to the universally-admitted conclusion that comets are neither more nor less than swarms of meteorites. Again, the resemblance between the spectra of comets and those of nebula suggests that these. also, are swarms, or aggregations, of meteorites. And we naturally infer that the stars with similar bright-line spectra must be collections of meteorites. From bright-line stars

we pass to those whose meteoritic origin is no longer to be recognised, all having blended together. Further, it is claimed that, by supposing variable and temporary stars to be due to the meeting and entanglement of two meteoritic swarms, we get a better explanation of the observed phenomena than any other hypothesis can give.

This meteoritic hypothesis supposes that the present material Universe was at one time in a state of cosmic dust," spread irregularly through space, and moving slowly in many directions. It is the original irregular distribution of the cosmic dust and its irregular movements which are the source of all the energy in the Universe. We have specimens of this cosmic dust in the chondroi, or spherules. of which many of the stony meteorites are built up. They are small round bodies of crystallised minerals, varying from microscopic dimensions to the size of a marble. Of course, these chondroi are not the first form in which matter existed. They are evidently due to chemical reactions, and we could frame several different hypotheses as to their origin and his

See "The Meteoritic Hypothesis," Macmillan, 1890; and Inorganic Evolution," Macmillan, 1900.

tory. But these would be speculations which could not, at present, be verified, and so we must content ourselves with the chondroi as the earliest form of matter known to us.

Through the action of gravitation much of the cosmic dust is supposed to have aggregated into meteorites. whose irregular movements were, in certain places, reduced to order; and so arose a number of meteoritic streams, or swarms. moving through space. Still, under the force of gravitation. each of these swarms got more and more dense, until, at last, collisions took place between the meteorites; light and heat were given out, and the swarm became a nebula. The heat produced by the collisions would, at first, be slight, but would gradually increase, until the whole of the solid material was resolved into vapour, and a star was formed. Concentration, however, would still go on, and the temperature of the star would rise, until, in time, the loss by radiation more than counterbalanced the gain by concentration, when the star would begin to cool. At last light would no longer be given off, and the star would end by becoming a dark cold body moving in space. Of course, some stars would attain a higher maximum temperature than others. and either a single or a double star might be the result of the condensation; but all would follow a somewhat similar development.

Now, as a matter of fact, the spectroscope shows us that stars in all these stages actually exist at the present day in the heavens. In some the temperature is increasing, in others it is decreasing; and, although small stars must run through their development quicker than large ones, this is quite insufficient to account for all the present differences. From which it follows that some of the stars are much older than others. The sun was amongst the earliest of formed stars. When it was born the sky must have presented an almost uniform blackness. There was no Milky-Way; no Orion nor Southern Cross; no Pleiades nor Dog-star. AH these, and many others, have been added since; not alto gether, but one after the other, through the long ages during which the sun was undergoing development. Judging by the relative ages of the stars, it seems probable that the process of concentration of the original cosmic dust commenced near the Solar System, and spread outwards to the MilkyWay. But, however this may be, the process is not yet over. Many nebulæ have not yet condensed into stars. Swarms of meteorites still traverse space, and, even in the neighbourhood of the Solar System, they are so abundant that the earth alone is estimated to collect more than twenty millions each day.

However, slow as the process of condensation is, it is not endless. In time all the meteoritic dust will be collected into stars or planets, and in time the law of dissipation of energy will bring all these bodies to a uniform temperature. So, at last, the movements due to the original unequal distribution of matter will cease, and the life of the universe will come to an end. We know of no process of rejuvenescence by means of which dissipation of energy, and the force of gravitation, might be counteracted. Several attempts have been made to refute the theory of dissipation of energy. but all have failed. The ether, which pervades space, is the only part of the Universe which shows no sign of evolution. It alone remains unchanged.

A casual glance at the stars gives us the impression of immutability. We still speak of the fixed stars in much the same way as our forefathers used to speak of the everlasting hills. But we know that they are not fixed. We know that the nearer stars, including the sun itself, are in swift movement; and we infer that all are so. But we can see no connection between their movements. Single stars, or

small groups of stars, are rushing through space in various directions, and we cannot detect any common centre of gravity which holds them in control. The stars have not yet attained the regularity of movement that gravitation must bring about in a very ancient system, and this idea of the comparative youth of the Universe is strengthened when we remember that large numbers of the primitive meteorites are still wandering in space uncondensed into stars. If it be true that the sun is one of the oldest stars in the Universe, and if, as geologists think, the earth is not more than a hundred millions of years old, then it may very well be that the creation of the cosmic dust out of which the stellar Universe has been formed, took place less than two hundred millions of years ago. But, although it may be possible to place a limit to the age of the Universe, we can fix no time for its duration. It is impossible to form an estimate of the hundreds of millions of years that will pass before the end approaches. Still, a time must come when all energy will be equilibrated; and when, possibly, the visible Universe may resolve itself into invisible, motionless ether.

In the Solar System we can study the development of a meteoritic swarm in greater detail. Here we find that the whole of the meteorites did not collect into a single mass but that several planets, as well as the sun, were formed simultaneously. It has been shown by Professor G. H. Darwin that the effect of many collisions among a swarm of meteorites would be to gradually eliminate orbits of great