256 | Notices of Books. (April, 
generalities ; for, unless a student has clear conceptions of indi- 
vidual phenomena, it is impossible for him to understand their 
mutual relations or the general conclusions that are based upon 
them.” To provide an account of these concrete physical facts, 
and to show how they may best be wrested from Nature, has 
been the object of Professor Weinhold in the book before us. 
He takes us through a course of elementary physics, and shows 
us, not only how to make the experiments, but also how to make 
the necessary apparatus. If anything, his descriptions appear 
sometimes ’to be too tediously minute, but for the beginner they 
are certainly not so. Here, for example, we have directions for 
boring a hole in glass—an operation which is frequently neces- 
sary in physical experiments :—‘‘ The hole is bored with a round 
file, of which the point is broken off, so that a round surface of 
from 2 to 3 m.m. in diameter is obtained. The edge of this 
round surface is used for drilling, the file being held with the 
right hand in a slanting direction, and the thumbs being kept 
quite close to the broken end of the file, in order to increase the 
pressure, and also to prevent the file from slipping through the 
finished hole and breaking the glass. File and glass must, 
during the operation, be frequently welted with water, or, better 
still, with oil of turpentine. After piercing the glass completely 
by the point, the whole is enlarged by slowly turning the file 
from right to left in the manner in which a screw is drawn, 
repeatedly moistening the orifice and the file.” The author truly 
says it is advisable to practise this operation first on pieces of 
broken glass; for, if ever patience be wanted, it is when one is 
engaged in boring a hole in glass, or endeavouring to render 
the double needle of a galvanometer astatic. Let us glance 
at the author’s treatment of any individual science; for example, 
heat. Omitting all theoretical matter, the author plunges at 
once into the subject; tells us that there is a particular sensation 
depending upon change of temperature, and that to the cause of 
this sensation is given the name Heat. Of the various effects 
of heat upon matter, expansion comes first, and this is illustrated 
by various means in the case of solids, liquids, and gases; and 
various experimental hints and cautions are given. An account 
of the thermometer follows, and rules for the conversion of 
degrees, and for determining the fixed points; then various 
effects of expansion, Prince Rupert’s drops and Bologna flasks ; 
anomalous expansion of water, absolute and apparent expansion, 
and the expansion of gases. A section is then devoted to 
melting and freezing, followed by evaporation and ebullition ; 
radiation and conduction ; specific and latent heat, and sources 
of heat. There is thus nothing new in the arrangement of 
subject matter, or indeed in the treatment of it, save that each 
experiment is minutely described, the necessary precautions 
and the conditions of success. The young student of physics 
will find this work a most useful companion. 
