etc.,
which have commonly been applied to both the effect and the agent
producing the effect have been rescued from this ambiguity.

RECENT ADVANCES in physics have been faithfully recorded, and the
relative practical importance of the various topics has been taken
into account. Among the new features are a full treatment of electric
lighting, and descriptions of storage batteries, methods of
transmitting electric energy, simple and easy methods of making
electrical measurements with inexpensive apparatus, the compound
steam-engine, etc. Static electricity, which is now generally regarded
as of comparatively little importance, is treated briefly; while
dynamic electricity, the most potent and promising physical element of
our modern civilization, is placed in the clearest light of our
present knowledge.

In INTEREST AND AVAILABILITY the _Introduction_ will, it is believed,
be found no less satisfactory. The wide use of the _Elements_ under
the most varied conditions, and, in particular, the author's own
experience in teaching it, have shown how to improve where improvement
was possible. The style will be found suited to the grades that will
use the book. The experiments are varied, interesting, clear, and of
practical significance, as well as simple in manipulation and ample in
number. Certain subjects that are justly considered difficult and
obscure have been omitted; as, for instance, certain laws relating to
the pressure of gases and the polarization of light. The
_Introduction_ is even more fully illustrated than the _Elements_.

IN GENERAL. The _Introduction_, like the _Elements_, has this distinct
and distinctive aim,--to elucidate science, instead of "popularizing"
it; to make it liked for its own sake, rather than for its gilding and
coating; and, while teaching the facts, to impart the spirit of
science,--that is to say, the spirit of our civilization and progress.

GEORGE E. GAY, _Prin. of High School, Malden, Mass._: With the matter,
both the topics and their presentation, I am better pleased than with
any other Physics I have seen.

R. H. PERKINS, _Supt. of Schools, Chicopee, Mass._: I have no doubt we
can adopt it as early as next month, and use the same to great
advantage in our schools. (_Feb. 6, 1888._)

MARY E. HILL, _Teacher of Physics, Northfield Seminary, Mass._: I like
the truly scientific method and the clearness with which the subject
is presented. It seems to me admirably adapted to the gr