A Class-Book of Chemistry

in which the Latest Facts and Principles of the Science are explained and applied to the Arts of Life and the Phenomena of Nature. A New Edition, entirely rewritten. By EDWARD L. YOUMANS, M. D. New York : D. Appleton & Co.

THOUGH Science has been often vaguely supposed to be something generically distinct from ordinary knowledge, yet the slightest consideration will suffice to show us that this is not the case. Scientific knowledge is only a highly developed form of the common information of ordinary minds. The specific attribute by which it is distinguished from the latter is quantitative prevision. Mere prevision is not peculiar to science. When the schoolboy throws a stone into the air, he can predict its fall as certainly as the astronomer can predict the recurrence of an eclipse ; but his prevision, though certain, is rude and indefinite : though he can foretell the kind of effect which will follow the given mechanical impulse, yet the quantity of effect—the height to which the stone will ascend, and the rapidity with which it will fall — is something utterly beyond his ken. The servant - girl has no need of chemistry to teach her, that, when the match is applied, the fire will burn and smoke ascend the chimney ; but she is far from being able to predict the proportional weights of oxygen and carbon which will unite, the volume of the gases which are to be given off, or the intensity of the radiation which is to warm the room : her prevision is qualitative, not quantitative, in its character. But when Galileo discovers the increment of the velocity of falling bodies, and when Dalton and De Morveau discover the exact proportions in which chemical union takes place, it is evident that knowledge has advanced from a rudely qualitative to an accurately quantitative stage ; and it does not admit of dispute that the progress of science is thus a progress from the indefinite to the definite.

From the point of view hero taken it would appear that during the present century no science has made such rapid and unprecedented strides as Chemistry; and its progress becomes all the more striking, when we consider the state of the science previous to the French Revolution. For centuries nothing had been done in it whatever. Besides the commonest previsions of every-day life, the ancients knew scarcely anything either of chemistry or physics, except that amber possessed attractive properties. The discovery of the strong acids by the Arabs Giafar and Rhazes, and of phosphorus by Bechil, are almost the only landmarks in the history of the science, until the discovery of oxygen and the destruction of the phlogistic theory by Priestley and Lavoisier, together with the introduction of the balance and the thermometer into the laboratory, rendered quantitative experiments possible. Since then its progress has been unexampled. The law of definite proportions, not long since disputed or unwillingly accepted, has been proved to hold even among organic compounds. A nomenclature has been invented and perfected, such as no other science can boast of, whether we consider the extent to which it facilitates practical operations, or its logical value as a means of mental discipline. Chemistry has also interacted with the different branches of physics, giving us the voltaic battery, the telegraph, and the wonderful results of spectrum-analysis. On the other hand, it has analyzed the proximate constituents of animal and vegetal structures, and has even gone far toward determining some of the conditions of organic existence ; while every one of the arts, whether æsthetic, therapeutic, or industrial, has received from it many and important suggestions.

In a science which advances so rapidly there is great need of popular books which shall clearly and succinctly present the very latest results of investigation, without burdening the reader with technical details. For some time there has been no such work in this country. To ascertain the newest discoveries, it has been necessary to consult the journals and memoirs of learned societies, the excellent works of Professor Miller being too cumbrous to be of much service either to the unscientific reader or to the general scholar. On the other hand, the text-books in common use have been positively detestable. The information furnished by many of them is worse than ignorance. We are tired of works on chemical physics which discourse of “ caloric ” and “ the electric fluid,”—of works on organic chemistry which ascribe the phenomena of life to “ a vital principle which overrides chemical laws.” A book at once clear, concise, and modern has long been the great desideratum.

This need is most amply supplied by the recent work of Dr. Youmans. Laying no claim to the character of an exposition of original discoveries, and thus keeping aloof from involved discussion, it is at the same time so lucid in its statements, so pertinent in its illustrations, and so philosophic in its reflections, as to invest with a new charm every subject of which it treats. The author deserves high praise for taking into account the circumstance that the reading public is not entirely composed of physicists and chemists. It has been too much the fashion for writers on scientific subjects to give definitions which can be rendered intelligible only by an intimate acquaintance with the very matters defined. It would be tedious to enumerate the countless absurd explanations given in elementary text-books of the phenomena of interference, polarization, and double refraction, — explanations as enigmatical as the inscriptions at Memphis and Karnak,— explanations useless to the optician because needless, and to the student because obscure. It would seem that subjects so simple and, beautiful as these could not be rendered difficult of comprehension, except by the most awkward treatment; and yet we know of no work previous to that of Dr. Youmans which does not utterly fail to give the general scientific reader any idea whatever of their nature and theory. Here, however, they are explained with clearness and elegance, and their bearing on the undulatory theory of light is distinctly shown. As other instances of most admirable exposition, we may call attention to the paragraphs on crystallization, on the atomic theory, on isomerism and allotropism, on diamagnetism, magnetic induction, and electric “ currents,” on the sources of heat, on the chemical and thermal spectra, on the correlation and equivalence of the forces, on the theory of ozone, on the exceptional expansion of water and the supposed complexity of its atom, on the structure of flame, on the constitution of salts, on the colloid condition of matter, on types and compound radicles, on the dynamics of vegetable growth and the production of animal power, and, above all, to the passage which describes the phenomena of latent heat. Throughout, in treating of these subjects, the author’s felicity of exposition never fails him. The most difficult phenomena are rendered perfectly easy of comprehension, and their mutual relations are not left out of account. Each set of facts is treated, not as forming an isolated body of truth, but as an integral portion of the complex and logically indivisible universe. In this respect Dr. Youmans’s work is far superior to the recent production of Dr. Hooker, in which, for example, the mere existence of such a doctrine as that of the correlation of forces is grudgingly noticed, and its ultimate significance entirely overlooked.

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 he 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 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 he 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 “either” 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.