tion of rules for restricting the play of combination among these elements, we can no longer, in the face of this stock of self-existent originals, allow the pretence of simplicity to be anything but an illusion.

Large as the atomist's assumptions are, they do not go one jot beyond the requirements of his case. He has to deduce an orderly and determinate universe, such as we find around us, and to exclude chaotic systems where no equilibrium is established. In order to do this he must pick out the special conditions for producing this particular kosmos and no other, and must provide against the turning up of any out of a host of equally possible worlds. In other words, he must, in spite of his contempt for final causes, himself proceed upon a preconceived world-plan, and guide his own intellect as, step by step, he fits it to the universe, by the very process which he declares to be absent from the universe itself. If all atoms were round and smooth, he thinks no such stable order of things as we observe could ever arise; so he rejects these forms in favour of others. By a series of such rejections he gathers around him at last the select assortment of conditions which will work out right. The selection is made, however, not on grounds of à priori necessity, but with an eye to the required result. Intrinsically the possibilities are all equal (for instance), of round and smooth atoms, and of other forms; and a problem therefore yet remains behind, short of which human reason will never be content to rest, viz. How come they to be so limited as to fence off competing possibilities, and secure the actual result? Is it an eternal limitation, having its "ratio sufficiens" in the uncaused essence of things; or superinduced by some power which can import conditions into the unconditioned, and mark out a determinate channel for the "stream of ten

dency" through the open wilds over which else it spreads and hesitates? It was doubtless in view of this problem, and in the absence of any theoretic means of excluding other atoms than those which we have, that Herschel declared them to have the characteristics of "manufactured articles." This verdict amuses Dr. Tyndall; nothing more. He twice* dismisses it with a supercilious laugh; for which perhaps, as for the atoms it concerns, there may be some suppressed "ratio sufficiens." But the problem thus pleasantly touched is not one of those which solventur risu; and, till some better-grounded answer can be given to it, that on which the large and balanced thought of Herschel and the masterly penetration of Clerk Maxwell have alike settled with content, may claim at least a provisional respect.

Having confined myself in this section to the Atomic Materialism, I reserve for the next the consideration of the Dynamic Materialism, and the bearings of both on the primary religious beliefs. To those-doubtless the majority in our time-who have made up their minds that behind the jurisdiction of the natural sciences no rational questions can arise, and from their court no appeal be made, who will never listen to metaphysics except in disproof of their own possibility, I cannot hope to say any useful word: for the very matters on which I speak lie either on the borders of their sphere, or in quite another. I am profoundly conscious how strong is the set of the Zeit-geist against me, and should utterly fail before it, did it not sweep by me as a mere pulsation of the Ewigkeitsgeist that never sweeps by. Nor is it always, even now, that physics shut up the mind of their most ardent and successful votary within their own province, rich and vast

* Belfast Address, p. 26. Fortnightly Review, Nov. 1875, p. 598.

as that province is. "It has been asserted," says Professor Clerk Maxwell, "that metaphysical speculation is a thing of the past, and that physical science has extirpated it. The discussion of the categories of existence, however, does not appear to be in danger of coming to an end in our time; and the exercise of speculation continues as fascinating to every fresh mind as it was in the days of Thales." "'*

II. THE DYNAMIC MATERIALISM.

It is curious to observe how little able is even exact science to preserve its habitual precision, when pressed backward past its processes to their point of commencement, and brought to bay in the statement of their "first truth." The proposition which supplies the initiative is sure to contain some term of indistinct margin or contents; and usually it will be the term least suspected, because most familiar. The student of nature takes as his principle that all phenomena arise from a fixed total of force in a given quantity of matter; and assumes that, in his explanations, he must never resort to any supposed addition or subtraction of either element. In adopting this rule he must know, you would say, what he means by "matter," and what by "force," and that he means two things by the two words. Ask him whence this principle has its authority. If he pronounces it a metaphysical axiom, you may let him go till he can tell you how there can be not simply an à priori notion of matter and notion of force, but also an à priori measure of each, which can guarantee you against increase or diminution of either. As standards of quantity are found only in experience, he will come back with a new

* Experimental Physics, Introductory Lecture, ad finem.

40

INDESTRUCTIBILITY OF MATTER.

answer, fetched from the text-books of science: that his principle is inductively gathered; in one half of its scope —viz., that neither matter nor force is ever destroyed— proved by positive evidence of persistence;-in the other half-viz., that neither is ever created-proved by negative evidence, of non-appearance. If now you beg him to exhibit his proof that matter is indestructible, he will in some shape reproduce the old experiment of weighing the ashes and the smoke, and re-finding in them the fuel's mass: his appeal will be to the balance, his witnesses the equal weights. Weight, however, is force: and thus, to establish the perseverance of matter, he resorts to equality of force. Again, when invited to make good the corresponding position, of the conservation of force, he will show you how, e.g., the chemical union of carbon and oxygen in the furnace is followed by the undulations of heat, succeeded in their turn by the molecular separation of water into steam, the expansion of which lifts a piston, and institutes mechanical performances: i.e. he traces a series of movements, each replacing its predecessor, and leaving no link in the chain detached. Movements, however, are material phenomena : so that to establish the persistence of force, he steps over to take counsel of matter. He makes assertions about each term, as if it were an independent subject: but if his assertion respecting either is challenged, he invokes aid from the other: and he holds, logically, the precarious position of a man riding two horses with a foot on each, hiding his danger by a cloth over both, and saved from a fall by dexterous shifting and exchange.

Nothing can be more unsatisfactory than a scientific proposition, the terms of which stand in this variable relation to each other. The first of them has been sufficiently fixed in discussing the Atomic conception. It remains to give

distinctness to the second. In order to do so, it will be simplest to follow into their last retreats of meaning the parallel doctrines of the "Indestructibility of Matter" and of the "Conservation of Energy." If our perceptions were so heightened and refined that nothing escaped them by its minuteness or its velocity, what should we see, answering to those doctrines, during a course of perpetual observation?

1. We should see the ultimate atoms; and if we singled out any one of them, and kept it ever in view, we should find it, in spite of "change of form," "always the same." A simple elementary atom," says Professor Balfour Stewart, “is a truly immortal being, and enjoys the privilege of remaining unaltered and essentially unaffected by the most powerful blows that can be dealt against it."* Here, then, we have alighted upon the "Matter" which is "indestructible."

2. These atoms might have been stationary; and we should still have seen them in their "immortality." But they are never at rest. They fly along innumerable paths: they collide and modify their speed and their direction: they unite they separate. However long we look, there is no pause in this eternal dance: if one figure ceases; another claims its place. As in the atoms, so in the molecules which are their first clusters, there is a state of continual agitation," "vibration, rotation, or any other kind of relative motion;"+ "an uninterrupted warfare going on—a constant clashing together of these minute bodies." In this unceasing movement among the "immortal" atoms we alight upon the phenomenon, or series of phenomena, de

*The Conservation of Energy, p. 7.

+ Theory of Heat, by J. Clerk Maxwell, p. 306.

+

Conservation of Energy, by Dr. Balfour Stewart, p. 7.