As we have scen, all that appears in motion, is transmutation or conversion of energy; accordingly it follows, that there is change of position, but no destruction of energy, or absolute disappearance of it from existence. This generalization is illustrated by a most attractive series of observations, introducing to a fuller knowledge of the laws of heat. The natural tendency of ordinary observation is to favor the opinion that when work has been done, energy is spent or lost. And this popular notion, which has a kind of accuracy, in so far as it is needful to make fresh draughts upon available resources, is favored by reference to the economy of our bodily existence constantly renewing its demand for fresh food supply. But this popular tendency is easily explained by the circumstance that ordinary observation makes much more account of the phenomena of motion, than of the development of heat as a direct consequence. The machinist can not, indeed, afford to make little of the consequences of friction; but the ordinary observer makes much more of mass, and complication of mechanical contrivance, and velocity of movement. From this he passes easily to the fabric, or other produc

tion, sent forth; and then he may occupy himself with calculations bearing on the expenditure for coals and labor, along with tear and wear of machinery. But scientific observation has concentrated much more on the evolution of heat, and out of this has come the completed theory of the laws of energy. In this way, it became matter of distinct calculation that friction and percussion convert energy into heat.

Along with these observations we have to remark upon an attendant conclusion, which has an important bearing on all speculation concerning the destiny of the universe. I refer to the fact that transmutation of energy involves a deterioration and dissipation of energy. As in the history of energy, improved position adds to the advantage for the doing of work, so transmutation tends to diminish the advantage or utility of the energy for human purposes. Thus the energy expended in working a machine gives return in a product of recognized value, but the energy spent in contending with friction generates heat which is of no practical value in respect of accomplished work. Or as the latter fact has been stated by Professor Balfour Stewart, friction proves

In

"itself to be, not the destroyer of energy, but merely the converter of it into some less apparent, and perhaps less useful form."* this connection, scientific observation was directed upon the appearance of heat simultaneously with the disappearance of visible energy. Gradually the conception dawned upon scientific observers that heat is a form of motion, and this has found general acceptance, although it is impossible to give direct proof of the doctrine. The conclusion has been supported by all the experiments of Davis, Rumford, Joule, Colding, and Helmholtz. This conception having been launched as to the probable explanation of heat, it immediately found, in accordance with the analogies of scientific thought, a greatly extended circle of application. Light and sound came to be classified with heat, as only different forms of motion. It would involve too extended a range to include here a detailed account of these experiments, or to consider what is involved in dissipation of energy, as bearing upon a still wider aspect of the order of things in the universe. I must, therefore, be content with the reference just given to

• The Conservation of Energy, p. 36.

the conception of heat as a form of molecular motion; and in doing so may revert to the consideration already adduced, that this is another doctrine of scientific belief, of which there is a constant tendency to increase the number, as science widens the range of its inquiries and speculations.

The outstanding general results of science as to the nature of energy are now before us. All observations concerning motion only present to view transmutations of energy, all of them imply that there is no such thing as the origin of energy, and no such thing as its extinction. There is indeed a constant tendency towards the degradation of energy, and a constant equalizing process which may bring to an end the present order of things in the universe. But the leading scientific conception with which we have specially to deal is that expressed in the phrase, "Conservation of energy," which must be regarded as completing our view of inorganic existence along with the other doctrine of the indestructibility of matter. As Professor Tait has expressed it,"The grand principle of conservation of energy, which asserts that no portion of energy can be put out of existence, and no amount

of energy can be brought into existence by any process at our command, is simply a statement of the invariability of the quantity of energy in the universe, a companion statement to that of the invariability of the quantity of matter.” *

The position is now reached at which it becomes possible to combine the results of scientific research as to matter and energy into a harmonious unity, with which to test the view of the world recognized by religious thought. Religion as an intelligent and devotional acknowledgment of a Supreme Being, involves a very clear and definite conception concerning the origin of the universe and its continuance. What is thus implied will be best indicated by negative as well as positive statements, in some such form as the following. First, negatively, the world we inhabit does not carry within it any explanation of the origin of its own existence; that is to say, neither the materials existing, nor the forces operating, are sufficient to account for its origin; neither can it have had existence without beginning. In positive form, the universe can be accounted for only by that which * Recent Advances of Physical Science, p. 17.