sible? I allow that we cannot in imagination represent it to our minds. Infinity told out, so to speak, is inconceivable. But is not a beginning of time equally inconceivable? A mind so metaphysical as that of Sir W. Hamilton thought an absolute beginning inconceivable. The infinite passing of time up to this present moment is, in fact, an infinite bounded on one side. The idea here meant to be conveyed may not perhaps be properly spoken of as that of an infinite. But still it is intelligible, and I ask is it impossible in fact? Let us take another illustration. Imagine a straight line indefinitely prolonged in both directions. Suppose a point moving uniformly along it in one direction always. This point may, I think, fairly represent the present moment, passing on out of the past into the future. Is it inconceivable that this point should have been so moving for ever? If it be not, why must there be a beginning in the analogue time? We can at least conceive the course of our point reversed, going back for ever.

I will not dwell longer on these arguments, drawn from highly abstract considerations. There may be others, but I think that we have considered enough as specimens, and I do not suppose that any others which might be produced would differ much in principle, or be found more satisfactory. Such

1 'Discussions on Philosophy and Literature,' Appendix I.

reasoning is not I believe popular now.

It is not

by such logical handling of abstract ideas that the popular philosophy seeks results. But there are, I must allow, certain arguments for the existence of God, founded on the most recent results of modern science, which are really kindred in principle. They seek to prove a creation, and therefore a creator, by showing, from the facts of the present universe, that it must have had a beginning. They fall, therefore, under the class of reasonings of which I am speaking, and I will accordingly notice them next.

PART IV.

The argument of which I shall speak first has its foundation in modern views as to force, or rather energy. The following account of it will, I fear, be tedious to anyone acquainted with those views; but my wish is to introduce such explanations as shall make the argument intelligible to those to whom the subject may be new.

I would begin by saying a few words as to the meaning of terms. Force is thought of by mathematicians as that which produces or changes motion in a body. They estimate force in two ways. First,

they speak of accelerating force, which they measure simply by the change which is made in a body's velocity. Second, they speak of moving force, a term which they use when the mass of the body acted upon is taken into account. Moving force they measure by the mass of the body multiplied into the change in its velocity or, what is the same thing, the accelerating force. It is further a convention that work done should be measured by the moving force, multiplied into the distance through which it acts. And it is proved, by the aid of the infinitesimal calculus, that this work done, thus measured, is equal to half the mass into the change in the square of the velocity. The product of the mass into the square of the velocity, is called in mathematical books vis viva, and, what concerns us more at present, half of it is the measure, as I have just said, of the power to do work, what is called kinetic energy. I would call attention to the designation kinetic, because we shall have presently to speak of another kind of energy, called potential. The kinetic energy, then, of a body is measured by one half of the product mass multiplied into velocity squared, and whatever it be, it is the power that does work, say, carries up a heavy body from the earth against gravitation, or forces a bullet into a block of wood. Now it is a great discovery of modern times that this kinetic energy is convertible,

according to fixed rules of equivalence, into things which at first sight seem to have nothing to do with motion, into heat, light, electricity, magnetism, chemical combination. Thus we have motion transformed into heat, according to the following rule. Take the quantity of water which weighs one pound avoirdupois in vacuo, at a temperature between 55° and 60° Fahrenheit. The amount of heat needed to raise the temperature of this water through 1° Fahrenheit is equivalent to the kinetic energy needed to raise 772 lbs. avoirdupois through I foot in our latitude, or, what would be the same, I lb. through 772 feet. We find that when motion is stopped, as by collision or friction, and when, therefore, kinetic energy at first sight seems to be destroyed, it is not really lost, but passes into some of these other forms, most commonly heat. Hence kinetic energy, once called into existence, is never destroyed. It may, however, be stored up in some latent form, as, for instance, when the energy in the sun's rays is used in the leaves of plants to chemically separate the carbon in the carbonic acid gas of the atmosphere from the oxygen, so as to supply material for the vegetable world. The energy thus used is, so to speak, stored up in the vegetables. And in this case it may be liberated again at a distant time by combustion of the vegetable matter. Kinetic energy, I repeat, is never destroyed; it passes into various

forms, and sometimes it is laid by, so to speak, in forms in which it may again cause motion, and so appear as kinetic energy. These changes in the forms of energy, and this preservation of its amount, are called respectively the transformation and conservation of energy. Kinetic energy may be in many ways produced. Whenever, in fact, the forces of the universe are producing motion, they are calling this energy into existence. Gravitation is constantly doing so on a stupendous scale. But for gravitation, or indeed any of these forces, to do this, there must be a distribution of matter in space. It must not be all accumulated in a mass. Gravitation, for instance, cannot produce kinetic energy in a stone lying on the earth's surface. The stone must be in a position to fall freely. Here we obtain the idea of potential energy-of that energy which the forces of the universe have not yet called forth into kinetic energy, but which the arrangements and collocations of the universe give them the opportunity of calling forth. If we call this energy just described potential energy, we see that the action of force is to add to the stock of kinetic what it takes from the stock of potential energy. And we see also in some cases, as in that mentioned of the vegetable world, or in the case of vapours raised by the sun's rays from the surface of the water to the sky, that kinetic energy is withdrawn back into potential, so as partially to recruit the