he 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
o