< A Philosophy of Materialisation (continued from page 11-347) >
engine is made use of for the performance of work, which work on removal from a system would necessitate the expenditure of other work, if the system were to be restored to its original condition of potentiality or work-doing ability. The reversible engine, an ideal construction due to Carnot, illustrates fully the nature of work which remains in a system as a part of its capital, so to say, and contrasts it with the work which is done on matter which is not in dynamical relation with that system. This subject is admirably treated in Professor Clerk Maxwell’s Theory of Heat and in Professor P. G. Tait’s Recent Advances in Physical Science.
It would therefore appear that during mediumistic exhibitions of power, we have no right to assume that there can ever be an absolutely reversible work of preparation; for though there may be a physiological application of the matter and energy of construction after the reversal, yet we cannot assume that it can ever do as high class work to the same extent, even though it were quantitatively identical after the operation. In speaking therefore in this paper, of phenomena indicative of reversible and irreversible expenditure this reservation is to be remembered. I will further add that when work, such as the movement of matter in space, is done, or other work which necessitates the immediate removal of available energy from the organism, a breach of continuity is implied, involving the separation of energy into free space, unlimited by any transcendental reference to a subjective form, whether that be time of conscious sensibility and intellectual change, or any lower theatre of subjectivity proper to animal life or organic processes.
If a man walk to the top of a hill and thereby gain energy of position, he may be able to execute a preconceived design, but he cannot use the energy of his position otherwise than as a link already forged in the chain of circumstances, relating to his personal exertions. If he throw himself over a precipice, the work done in gaining that elevation would be returned in the equivalent of heat and vibrations consequent upon shock of arrest through contact with the ground. His descent under the pull of gravity might be employed to do useful work on a mass of matter other than his own body, to which the mechanical work he has dune can never be returned through a direct transformation of energy. If after gaining the top of the hill he turn to go down again, he must actually undo by positive work the work done in going up the hill, for he has to let himself down against the constantly acting pull of gravity, the rate and manner of his descent determining how shock vibrations should be divided between him and the ground. In any case, energy corresponding to the work done in going up and coming down again is wholly dissipated and lost. But has no good been derived from the work so lost? Quite the contrary, for he can repeat the performance next day. This introduces us to the useful idea, work of preparation, which determines the perfection of functional activity. To the working body, it is a matter of indifference whether the work of preparation continue to exist, for a greater or less time, as useful work, before being dissipated, for work of preparation, regarded as such, is superficial, is simply a dynamic link connecting the past and future functional activities. By considering the above cases, we see that there is a continual expenditure by the animal body in stretching a spring held horizontally, holding it open and returning it slowly to its original configuration, while if it be permitted to return by its own elasticity, energy will be dissipated through the air and heat vibrations follow sooner or later, on the shock of return; so that, if one end be held in the hand of the operator the jar will be communicated to his body, when part of the energy originally expended as mechanical work will be returns to it and ultimately dissipated as heat.
I will now take a purely imaginary case, which may be used to lead up to a principle without burdening ourselves with details. If by an effort of will the human body could for a time be lengthened out, or the arm be extended across the room against a force acting from within, it is easy to understand that in the act of protrusion (always remembering that no natural laws are violated) potential energy would be consumed, which in some equivalent form would be restored to the body from which it was derived on the return of that body to its normal configuration, but only on the condition that the restoration took place under the influence of its own unopposed force of restitution. This arm when so pushed out is imagined to be functionally perfect so that it can perform any of the duties of an arm, but with a wider sweep; all such work, which is of the nature of irreversible muscular work, is to be paid for as ordinary muscular work is paid for, that is in terms of energy transformed, for it must be remembered that the conservation of energy is unquestioned, so that all consideration of the work done by this arm may be left out of sight as being common and natural enough, our attention being directed to the consequences involved in supposing the existence of such a thing as an elastic arm obedient to the will, which in whole or in part returns to the ordinary state after a while. If the return take place slowly and against a constantly exerted strain, which it just overcomes, we can learn nothing from the consideration of our case, for it would be similar to that of a man marching up to the top of a hill and then marching down again; one continual expenditure of the same kind would be demanded, and we could draw no inference but that the animal body paid for all the pressure exerted from its store of energy. But if the return to original configuration take place under the action of forces of restitution, and do not demand a continuous expenditure of work, the shock of return restores the equivalent of the energy expended in the forced extension. If this take the form of heat in the body, so far there has been no loss, and the restored heat is simply the equivalent of the mechanical power exerted. There is no occasion to mention the expenditure of maintenance in any unchanged configuration or position, which would all be represented by energy dissipated in the form of heat, I presume, as when muscle holds a weight fixed against gravity, but without moving it. This expenditure like that of actual work would be irreversible. I feel justified in borrowing a suggestion from that side or function of the muscular system, which does not relate to the movement of solid matter in space, i.e., from the necessary relationship existing between muscular contraction and animal heat. When first elongation took place in our hypothetical case, with an expenditure of energy, not muscular according to our supposition, will* alone in our imaginary case operating as a directive agent on the chemical affinities of the body, but subject to the law of the conservation of energy, we might suppose that the temperature of the body would fall below the natural standard, or that the temperature remaining the same a molecular change representing an alteration of specific heat would take place, or that the <... continues on page 11-349 >
* That is to say where Will conscious or otherwise would bear the same relation to the new instrument that voluntary command to move or stay bears to the muscular system. That there is already such an agent constantly at work in the body supervising its myriad details we all know.