selves as antecedent and consequent events. The events of history seem to come in chains, one link drawing on the next. So impressed have some philosophers been with this appearance of concatenation among events, that they have attempted to define causation itself in terms of succession, and they have thus brought great confusion into the science of inductive logic.

Perhaps it may be easier to define the difficult word Cause, and to show the relation of causation and succession, in connection with a concrete example. We will, therefore, take an instance classic in the history of inductive science, one of the experiments of the illustrious Count Rumford upon heat. The illustration will be useful not only here but in subsequent chapters, and it is so interesting that we will give it at length, and in the Count's own words.

"Being engaged lately in superintending the boring of cannon in the workshops of the military arsenal at Munich, I was struck with the very considerable degree of heat which a brass gun acquires, in a short time, in being bored; and with the still more intense heat, much greater than that of boiling water, as I found by experiment, of the metallic chips separated from it by the borer. From whence comes the heat actually produced in the mechanical operation above-mentioned? .

...

"... Taking a cannon, a brass six-pounder, cast solid, and rough as it came from the foundry, and fixing it horizontally in the machine used for boring, and at the same time finishing the outside of the cannon by turning, I caused its extremity to be cut off; and, by turning down the metal in that part, a solid cylinder was formed, 7 inches in diameter, and 9 inches long; which, when finished, remained joined to the rest of the metal, that which, properly speaking, constituted the cannon, by a small cylindrical neck, only 2 inches in diameter, and 3 inches long. This short cylinder, which was supported in its horizontal position, and

turned round its axis, by means of the neck by which it remained united to the cannon, was now bored with the horizontal borer used in boring cannon; but its bore, which was 3.7 inches in diameter, instead of being continued through its whole length, 9.8 inches, was only 7.2 inches in length; so that a solid bottom was left to this hollow cylinder, which bottom was 2.6 inches in thickness.

"The cylinder being designed for the express purpose of generating heat by friction, by having a blunt borer forced against its solid bottom at the same time that it should be turned round its axis by the force of horses, in order that the heat accumulated in the cylinder might from time to time be measured, a small round hole, 0.37 of an inch only in diameter, and 4.2 inches in depth, for the purpose of introducing a small cylindrical mercurial thermometer, was made in it, on one side, in a direction perpendicular to the axis of the cylinder, and ending in the middle of the solid part of the metal which formed the bottom of its bore.

"Exper. 3.-A quadrangular oblong deal box, water-tight, 11 English inches long, 9 inches wide, and 9 inches deep, being provided, with holes or slits in the middle of each of its ends, just large enough to receive, the one, the square iron rod to the end of which the blunt steel borer was fastened, the other, the small cylindrical neck which joined the hollow cylinder to the cannon; when this box was put into its place it was fixed to the machinery, in such a manner that its bottom being in the plane of the horizon, its axis coincided with the axis of the hollow metallic cylinder; it is evident, from the description, that the hollow metallic cylinder would occupy the middle of the box, without touching it on either side; and that, on pouring water into the box, and filling it to the brim, the cylinder would be completely covered, and surrounded on every side, by that fluid. And further, as the box was held fast by the strong square iron rod which passed, in a square hole, in the centre of one of its ends, while the round or cylindrical neck, which joined the hollow cylinder to the end of the cannon, could turn round freely on its axis in the round hole in the centre of the other end of it, it is evident that the machinery could be put in motion, without the least danger of forcing the box out of its place, throwing the water out of it, or

deranging any part of the apparatus. Everything being ready, I proceeded to make the experiment I had projected, in the following manner.

"The hollow cylinder having been previously cleaned out, and the inside of its bore wiped with a clean towel till it was quite dry, the square iron bar, with the blunt steel borer fixed to the end of it, was put into its place; the mouth of the bore of the cylinder being closed at the same time, by means of the circular piston, through the centre of which the iron bar passed. The box was then put in its place, and the joinings of the iron rod, and of the neck of the cylinder, with the two ends of the box, having been made water-tight by means of collars of oiled leather, the box was filled with cold water (viz., at the temperature of 60°), and the machine was put in motion. The result of this beautiful experiment was very striking, and the pleasure it afforded me amply repaid me for all the trouble I had had, in contriving and arranging the complicated machinery used in making it. The cylinder, revolving at the rate of about 32 times in a minute, had been in motion but a short time, when I perceived, by putting my hand into the water, touching the outside of the cylinder, that heat was generated; and it was not long before the water which surrounded the cylinder began to be sensibly warm. At the end of 1 hour, I found, by plunging a thermometer into the water in the box (the quantity of which fluid amounted to 18.77 lb. avoirdupois, or 24 wine gallons), that its temperature had been raised no less than 47 degrees, being now 107° of Fahrenheit's scale. When 30 minutes more had elapsed, or 1 hour and 30 minutes after the machinery had been put in motion, the heat of the water in the box was 142°. At the end of 2 hours, reckoning from the beginning of the experiment, the temperature of the water was found to be raised to 178°. At 2 hours 20 minutes it was at 200°; and at 2 hours 30 minutes it actually boiled.

"It would be difficult to describe the surprise and astonishment expressed in the countenances of the by-standers, on seeing so large a quantity of cold water heated, and actually made to boil, without any fire. Though there was, in fact, nothing that could justly be considered as surprising in this event, yet I acknowledge fairly that it afforded me a degree of childish pleasure, which,

were I ambitious of the reputation of a grave philosopher, I ought most certainly rather to hide than to discover." 1

Here is a phenomenon the heat of the water in Count Rumford's box. Let us inquire now what we are doing when we seek for its cause.

sense.

Plainly the motion of the cylinder was an antecedent of the heat in the water in some pre-eminent and unique Heat is an energy; it could not appear in the water unless it passed out of some other material in which it previously existed as motion, or in some other mode. We know this by a very broad primary induction. Indeed, we here come upon the grand generalization of the conservation, or, to use a better word, the

persistence, of energy. A multitude of experiences have led men to believe that whenever energy newly appears, it has existed previously in another mode or in other materials. The necessary antecedent of energy in one mode or one body is the same energy in a previous mode or in a different body. All machinery is contrived on this principle; at some point energy is introduced, and it is then transferred or transformed, so that we get light, heat, electricity or motion, as desired. From the standpoint of the physicist the whole cause of the heat of the water was the motion of the cylinder. The degree of heat gained by the one was exactly measured by the amount of motion lost by the other. There was only a transfer of energy. When in popular language we say that the motion is the cause of the heat, the physicist says that the motion is the heat, only in another mode. The law of causation, when applied to energy, is only the fact of persistence.

1 Phil. Trans. Royal Soc. of London, vol. xviii, pp. 278–282.

When we say that energy here must have had a cause, we only mean that, having no reason to think that new energy has been added to the world, we must consequently assume that this apparently new energy is only the old in a new mode. When, therefore, we inquire for the cause of energy, we may be merely inquiring, Where and in what mode was this energy previously? The answer to the question names the Energetic Cause. If it be asked, What was the cause of the motion in the cylinder? the answer is, The motion of the horses. The energy might be further traced through physiological action in the bodies of the horses, and then through physiological action in the growth of the grain and hay upon which they had fed, until at last we should reach the sun's light and heat. One thing is now agreed upon, that the stream of energy in the world, like the Nile in the desert, receives no tributaries, but simply flows on identical with itself, its transformations depending upon the qualities and collocations of

matter.

But why did motion in the cylinder become heat in the water? Here a cause is demanded in a different sense. The inquiry is for those properties and collocations of matter which occasioned a transformation. The arrangement was such that motion could not be communicated from the cylinder to any other part of the apparatus; the motion, therefore, according to a permanently coexisting property, transformed itself into heat. The different properties of energy and the different properties of the several sorts of matter in relation to energy, we know by primary inductions which cannot be resolved into simpler generalizations; they