s is to be preceded by a prefatory discourse on
"the objects and advantages" of the branch of knowledge which is treated
of in the series or cabinet. Thus, the work before us is such a volume
for the Cabinet of _Natural Philosophy_; that for History is
promised by Sir James Mackintosh; and that for the Useful Arts, by the
Baron Charles Dupin. The present _Discourse_ is by J.F.W. Herschel,
Esq., A.M. It is divided into three parts:--1. On the general nature and
advantages of the study of Physics. 2. The rules and principles of
Physical Science, with illustrations of their influence, in the history
of its progress. 3. The subdivision of Physics. These parts are divided
into chapters, and these chapters again divided into sectional
illustrations, of which latter there are nearly four hundred. Such an
arrangement can hardly fail to attract the listless reader. The style is
lucid and popular, and the writer's reasonings and bearings are brought
out with much point and vigour. Even a drawing-room reader must be
caught by their attractions, and no better means was probably ever
devised for bringing superficial readers into the way of knowledge, and
setting forth its pleasantness. It has been said that such works as the
present satisfy the reader, and disqualify him for the study of science.
This opinion is hardly worth controverting: since that mind must be weak
indeed which would not be _stimulated_ as well as gratified in this
case; and it is still more improbable that the great truths of science
should at once take root in such a barren soil without any preparation
for their reception.

We conclude with a few specimen extracts. The _how_, the _why_, the
_wherefore_, and the because, of such wonders as they relate to, belong
rather to the treatises themselves.

_Mechanical Power of Coals._

It is well known to modern engineers, that _there is virtue_ in a
bushel of coals properly consumed, to raise seventy millions of pounds
weight a foot high. This is actually the _average_ effect of an
engine at this moment working in Cornwall.

The ascent of Mont Blanc from the Valley of Chamouni is considered, and
with justice, as the most toilsome feat that a strong man can execute in
two days. The combustion of two pounds of coal would place him on the
summit.

_The Wonders of Physics_.

What mere assertion will make any man believe that in one second of
time, in one beat of the pendulum of a clock, a ray of light travels
o