• Matter may change its form and its chemical composition by rearrangement of its molecules or of its elementary atoms, but it cannot be de stroyed; forces inhere and are persistent as characteristics of all matter and cannot be sep arated therefrom; energy, like matter, is con stant in its total quantity in the universe and may be transferred and transformed, but cannot be extinguished. Transformation of energy, as of thermal into dynamic or mechanical, is sim ply the change of the kind of mass affected and consequent alteration of the kind of motion due to its action. A shot from a gun, stopped in its rapid flight by impact on the target, if not frac tured, will exchange the thousands of foot-tons of mechanical energy sustaining its flight for precisely the same quantity of molecular mo tion and energy. Similarly, were a shot heated to a high temperature and then were all its molecules by some conceivable process of steer ing each into its path, made to take up simul taneously a definite rectilinear motion, it would become absolutely cold and would fly out into space with a dynamic mass-energy precisely equal and, in fact, with the identical energy at first displayed as molecular. The heat-engine is a device for bringing about such a change for industrial purposes.
The laws of energetics, as usually enunciated, are: I. The Lam of Persistence. a of ConserveSox of Flurry, namely: Existing energy can never be annihilated; and the total energy, actual and potential, of any isolated system can never change.
This is evidently a corollary of that grander law, asserting the indestructibility of all the work of creation, which has already been enunciated.
2. The Low of Dissipation, or of Degradation of Energy, namely: All energy tends to diffuse itself throughout space, with a continual lose of intensity, with what seems, now, to be the inevitable result of complete and uniform dispersion throughout the universe, and consequently of entire loss of availability.
It is only by differences in the intensity of energy, and the consequent tendency to forcible dispersion, that it is possible to make it available in the production of work.
3. The Lam of Transformation of Enemy, namely: Energy may be transformed from one condition to another, or from any one kind or state to any other; changing from mass energy to molecular energy of any kind, or from one form of molecular energy to another, with a definite quentivatence.
Thermodynamics, being a restricted ener getic, in which only two energies, thermal and dynamic, are comprehended, its laws are, funda mentally, identical with the preceding and the enunciation just adopted is entirely accurate in this restricted science.
• The Laws of Thermodynamics, in the special forms considered best for the purposes of the thermodynamist, are corollaries of the laws of energetics and of Newton's laws, which are a different method of expression of the same fundamental principles. They are usually stated thus: The value of the mechanical equivalent of heat has been taken as first adopted by Joule, although recent and most carefully conducted investigations indicate a .value higher by perhaps 1 per cent, to be more accurate. Many existing tables, and much work done in this field to date, have, how ever, been based upon Joule's figure, 772 foot-pounds, 423 kilogrammetres. The figure, above given, 778 or 427, is now, however, generally accepted.
2. The total of any single effect of any given quantity of heat acting in any thermodynamic operation is proportional to the total amount of heca-msergi so Gain.
This principle is substantially that first accepted by Rankine as the second law. Actually energy of vibration is understood.
Thus, of the whole quantity of heat passing from the heater to the working substance, one part is always trans muted into mechanical work, or energy; while the remainder goes to the refrigerator, and the ratio of the one quantity to the other is perfectly definite.
Professor Wood expresses this law thus: " If lathe heat absorbed be at one temperature, and that rejected be at one lower temperature, then will the beat which IS transmuted into work be to the entire heat absorbed in the same ratio as the difference between the absolute tempera tures of source and refrigerator is to the absolute temperature of the source." The second law finds important application simply in enabling us to ascertain the total quantity of work, external and internal, requited to produce changes of volume and energy in fluids, like the vapors, in which we cannot measure directly the internal forces and internal work.
If the change of sensible heat be called dS, that of " latent " heat, dL, and of external work, dt. I, then the first law of thermodynamics is expressed by the equations: 1=dS + F dU (A) and dH=dS (B) dil=dE-1-dU where, in the last two expressions, dE = dS dL, and is the variation of ener8Y, actual and potential; while dW = dL d U, and is the total work done, externally and internally. These are primary and general equations.
The quantity E is often called the intrinsic energy of the substance; L is evidently a potential energy; while S is a form of molecular kinetic, or actual, energy, which may sometimes be regarded as also in a sense potential.