Far different is Dr. Youmans's treatment of the same doctrine. Indeed, we think that the chapters on chemical physics form the most interesting portion of his work, and their value consists chiefly in the constant reference to the modern ideas of force which pervades them. In a work intended for the education of youth, such a feature cannot be too highly praised. It is time that the old material superstitions about force were eradicated from men's minds, and as far as possible from their language. It is already more than half a century since Count Rumford demonstrated the immaterial nature of heat, and Young established the undulatory theory of light,—ideas which had germinated two hundred years ago in the lofty minds of Huygens and Hooke. Since then have been discovered the polarization and interference of heat, the triple constitution of the solar ray, the identity of magnetism and electricity, the polar nature of chemical affinity, the optical polarities of crystals, and the interaction of magnetism and light. Since then the once meagre and fragmentary science of physics has become one of the grandest and richest departments of human thought; and the illustrious names of Helmholtz, Joule, and Mayer, of Grove, Faraday, and Tyndall, may be fitly named beside those of the leading thinkers of past ages. The physical forces are no longer to be looked upon as inscrutable material entities,—forms of matter imponderable, and therefore inconceivable; but they have been shown to be diverse, but interchangeable modes of molecular motion, omnipresent, ceaselessly active. The wondrous phenomena of light, heat, and electricity are seen to be due to the rhythmical vibration of atoms. There is thus no such thing as rest: from the planet to the ultimate particle, all things are endlessly moving: and the mystic song of the Earth-Spirit in "Faust" is recognized as the expression of the sublimest truth of science:—
"In Lebensfluthen, im Thatensturm,
Wall' ich auf und ab, webe hin und her,
Geburt und Grab,
Ein ewiges Meer,
Ein wechselnd Weben,
Ein glühend Leben,
So schaff' ich am sausenden Webstuhl der Zeit,
Und wirke der Gottheit lebendiges Kleid."
In a discussion containing so much that is noble, however, we are sorry to observe that Dr. Youmans is betrayed into using the current expressions concerning an "ether" which is supposed to be the universal vehicle for the transmission of molecular vibrations. We are told, that, while "the vibrations of a sonorous body produce undulations in the air," on the other hand, "the vibrations of atoms in a flame produce undulations in the ether." We would by no means charge Dr. Youmans with all the consequences naturally deducible from such a statement. We believe that he uses the term "ether" simply to render himself more intelligible to those who have been wont to make use of it to facilitate their thinking. Such an object is highly praiseworthy, and is too often left out of sight by those who write elementary works. But the good service thus rendered is far more than counterbalanced by the host of erroneous conceptions which at once arise at the introduction of this luckless term. This notion of an "imaginary ether" should be at once and forever discarded by every writer on physics. The very word should be remorselessly expunged from every discussion of the subject. It is one of the most baneful words in the whole dictionary of scientific terminology. It stands for a fiction as useless as it is without foundation. It is useless because superfluous, and not needed in order to account for the phenomena. An ether is no more necessary in the case of light than it is in the case of sound. Thermal vibrations are the oscillations of atoms, not the undulations of an ether. If it be urged that rays of light and heat will traverse a vacuum, we reply, that the much-derided aphorism, "Nature abhors a vacuum," is as true at this day as it was before Torricelli's experiment. A perfect vacuum has never been produced; and if it were to be produced, the ether must be excluded, else it would be no vacuum, after all. For, if there were such a thing as an ether, it must of course be some form of matter; nobody ever claimed for it the character of motion or force. If it be considered as matter, then, we are confronted with new difficulties; for all matter must exert gravitation. Weight is our sole test of the very existence of matter; it is the balance which has proved that nothing ever disappears. Imponderable matter is no more possible than a triangular ellipse. Away, then, with such a mischief-breeding conception! Let this last-surviving fetich be ousted from the fair temple of inorganic science. Undulations have been measured and counted; quantitative relations, like those expressed in Joule's law, have been established between them; but an "ether" has never yet been the object of human ken.
We have expressed ourselves thus emphatically upon this all-important point, in order to warn the reader of Dr. Youmans's book against drawing conclusions which the author himself evidently does not mean to convey. No clear ideas can ever be entertained in physics until this anomalous "ether" is excommunicated; and therefore we wish it had been banished from this excellent treatise. We differ also very widely from the author's views of animal heat, but have not space to enter upon the discussion. With these exceptions we know of nothing in the work that could be improved. It is an honor to American science, and fully merits a more exhaustive examination than we have here been enabled to bestow upon it.
Strategy and Tactics. By General G.H. DUFOUR, lately an Officer of the French Engineer Corps, Graduate of the Polytechnic School, and Commander of the Legion of Honor; Chief of Staff of the Swiss Army. Translated from the latest French Edition, by WILLIAM R. CRAIGHILL, Captain U.S. Engineers, lately Assistant Professor of Civil and Military Engineering and Science of War at the U.S. Military Academy. New York: D. Van Nostrand.
The author of this work is a distinguished civil and military engineer and practical soldier, who, in all military matters, is recognized as one of the first authorities in Europe. His history is especially interesting to Americans, since not many years ago he played a prominent part in the suppression of a rebellion which, in many features, exhibited a remarkable similarity to the one with which our own Government is contending. We refer to the secession of the seven Swiss cantons forming the Sonderbund, which, like the insurrection of the Southern States, was a revolt of reactionary against liberal principles of government; it was likewise the fruit of a well-organized and long-matured conspiracy, which only delayed an open outbreak until all its preparations were adequately perfected for a formidable resistance. The issue of the contest was what we may hope will be that of our own,—the triumph of free principles, and the complete reëstablishment of the authority of the legitimate Government on a firmer basis than it had before occupied.
General Dufour was born at Constance, of a family of Genevese origin. Having acquired his early education at Geneva, where he devoted his attention chiefly to mathematics, he entered the Polytechnic School at Paris, was commissioned two years afterwards in the corps of Engineers, and served in the later campaigns of Napoleon, where he rose to the rank of captain. He afterwards entered the Swiss Federal service, in which he became colonel, chief of the general staff, and quartermaster-general. At later periods he has held the less active, but equally responsible and honorable positions of superintendent of the triangulation of Switzerland on which the topographical map of the country is based, and chief instructor of engineering in the principal military school of the Republic, at Thun.
When, in 1847, the Swiss Diet determined to dissolve the Sonderbund, which had at length committed the overt act of treason, General Dufour was appointed commander-in-chief of the Federal army. A few days after the call for troops was issued, he found himself at the head of an army of one hundred thousand men, and immediately entered actively upon the work before him. His dispositions were skilful and his movements rapid. He adopted with success the "anaconda" system of strategy, and hemmed in the insurgents at every point, closing in the mountain-passes, and completely isolating them. After six days of active campaigning the Canton of Freyburg was subdued; nine days afterwards Luzerne submitted; the other rebellious cantons were quick to yield; and in eighteen days from the commencement of active operations, and twenty-three days from the issue by the Federal Diet of the decree of coercion, the rebellion was extinguished so completely that no murmur of treason has since been heard in the Republic. So rapidly was the whole accomplished, that foreign powers had not time to intervene; and it is said, that, when the French messenger went to seek the insurgents with his proposals, they were already fugitives. In honor of his services in this contest, the Federal Diet voted General Dufour a sabre of honor and a donative of forty thousand francs.
General Dufour's "Strategy and Tactics" is evidently the fruit of an attentive study of the best examples and authorities of all ages. He has avoided mere theories and fine writing, and has aimed to present a work practical in its treatment and application. The lessons of history have been his guide; his precepts are fortified by pertinent examples from the campaigns of the best generals, and we may study them with confidence that when put to the actual test they will not fail.
The distinction between strategy and tactics, not always clearly understood, is in substance drawn thus by General Dufour. Strategy involves general movements and the general arrangement of campaigns, depending chiefly upon the topographical features of the country which is the scene of operations,—while tactics relate to the minor details of campaigns, as the disposition for marches and battles, the arrangement of camps, etc. Strategy depends upon circumstances fixed in their nature, and is the same always and everywhere; but tactics must be modified to suit degree of skill, arms, and manner of fighting of the combatants. Hence, "much instruction in strategy may be derived from the study of history; but very grave errors will result, if we attempt to apply in the armies of the present day the tactics of the ancients. This fault has been committed by more than one man of merit, for want of reflection upon the great difference between our missile weapons and those of the ancients, and upon the resulting differences in the arrangement of troops for combat." Our own military leaders have not entirely avoided mistakes of this kind in the conduct of the present war.