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 aesthetic, 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 “calorie” 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