We should be unreasonable to demand the sympathy of those classes which have everything to lose from the extension of the self-governing principle. What we have to thank them for is the frankness with which they have betrayed their hostility to us and our cause, under circumstances which showed that they would ruin us, if it could be done safely and decently. We shall never be good friends again, it may be feared, until we change our eagles into sovereigns, or they change their sovereigns for a coin which bears the head of Liberty. But in the mean time it is a great step in our education to find out that a new order of civilization requires new modes of thought, which must, of necessity, shape themselves out of our conditions. Thus it seems probable, that, as the first revolution brought about our industrial independence of the mother-country, not preventing us in any way from still availing ourselves of the skill of her trained artisans, so this second civil convulsion will complete that intellectual independence towards which we have been growing, without cutting us off from whatever in knowledge or art is the common property of Republics and Despotisms.
REVIEWS AND LITERARY NOTICES.
Heat considered as a Mode of Motion; being a Course of Twelve Lectures delivered at the Royal Institution of Great Britain, by JOHN TYNDALL, F.R.S., Professor of Natural Philosophy in the Royal Institution. New York: D. Appleton & Co.
The readers of the "Glaciers of the Alps" have made the acquaintance of Professor Tyndall as an Alpine adventurer, with a passion for frost and philosophy, and a remarkable ability both in describing his mountain-experiences and in explaining the interesting phenomena which he there encountered. All who have read this inimitable volume will testify to its rare attractions. It is at once dramatic and philosophic, poetic and scientific; and the author wins our admiration alike as a daring and intrepid explorer, a keen observer, a graphic delineator, and an acute and original investigator.
In the new work on Heat we are introduced to Professor Tyndall upon the lecturing-platform, where he follows up some of the inquiries started in the "Glaciers" in a systematic and comprehensive manner. His problem is, the nature and laws of Heat, its relation to other forms of force, and the part it plays in the vast scheme of the universe: an imposing task, but executed in a manner worthy of the gifted young successor of Faraday as Professor of Natural Philosophy in the Royal Institution of Great Britain.
A comparison of the volume before us with any of the previously published treatises on Heat will afford a striking and almost startling proof of the present activity of inquiry, and the rapid progress of scientific research. The topics treated are the same. The first seven lectures of the course deal with thermometric heat, expansion, combustion, conduction, specific and latent heat, and the relation of this force to mechanical processes; while the remaining five treat of radiant heat, the law and conditions of its movement, its influence upon matter, its relations to other forces, terrestrial and solar radiation, and the thermal energies of the solar system. But these subjects no longer wear their old aspect. Novel questions are presented, starting fresh trains of experiment; facts assume new relationships, and are interpreted in the light of a new and higher philosophy.
The old view of the forces, which regarded them as material entities, may now be regarded as abandoned. Light, Heat, Electricity, Magnetism, etc., which have hitherto been considered under the self-contradictory designation of "Imponderable Elements," or immaterial matter, are now, by common consent, beginning to be ranked as pure forces; having passed through their material stage, they are regarded as kindred and convertible forms of motion in matter itself. The old notions, that light consisted of moving corpuscles, and that heat, electricity, and magnetism were produced by the agency of various fluids, have done good service in times past; but their office was only provisional, and, having served to advance the philosophy of forces beyond themselves, they must now take rank among the outgrown and effete theories which belong to the infantile period of science. This change, as will be seen, involves the fundamental conceptions of science, and is nothing less than the substitution of dynamical for material ideas in dealing with the phenomena of Nature.
The new views, of which Professor Tyndall is one of the ablest expositors, are expressed by the terms "Conservation and Correlation of Forces." The first term implies that force is indestructible, that an impulse of power can no more be annihilated than a particle of matter, and than the total amount of energy in the universe remains forever the same. This principle has been well characterized by Faraday as "the highest law in physical science which our faculties permit us to perceive." The phrase "Correlation of Forces" is employed rather to express their mutual convertibility, or change from one to the others. Thus, heat excites electricity, and, through that force, magnetism, chemical action, and light. Or, if we start with magnetism, this may give rise to electricity, and this again to heat, chemical action, and light. Or we can begin with chemical action, and obtain the same train of effects.
It has long been known that machines do not create force, but only communicate, distribute, and apply that which has been imparted to them, and also that a definite amount of fuel corresponds to a definite amount of work performed by the steam-engine. This means simply that a fixed quantity of the chemical force of combustion gives rise to a corresponding quantity of heat, and this again to a determinate amount of mechanical effect. Now this principle of equivalency is found to govern the transmutations of all forms of energy. The doctrine of the conservation and correlation of forces has been illustrated in various ways, but nothing has so powerfully contributed to its establishment as the investigation of the relations of heat to mechanical force. Percussion and friction produce heat. A cold bullet, struck upon an anvil by a cold sledge-hammer, is heated. Iron plates, ground against each other by water-power, have yielded a large and constant supply of heat for warming the air of a factory in winter; while water inclosed in a box, which was made to revolve rapidly, rose to the boiling-point. What, now, is the source of heat in these cases? The old caloric hypothesis utterly fails to explain it; for to suppose that there is an indefinite and inexhaustible store of latent heat in the rubbing iron plates is purely gratuitous. It is now established, that the heat of collision, and of friction depends, not upon the nature of the bodies in motion, but upon the force spent in producing it.