May 23, 1884.] 
and to the personal characters of discoverers. 
His text-book provides the pupil with the meat 
of the subject: the side-dishes, dessert, etc., 
must be furnished by the teacher. 
The book is an octavo volume of about six 
hundred pages, — not larger than several well- 
known treatises in general use. Only an ele- 
mentary mathematical training is assumed ; so 
elementary, in fact, that the author has thought 
it desirable to define the well-known constant 
az, which he does in a note. Let no one be 
deceived by this, however: the student will 
discover, as he progresses, that he must know 
his elementary mathematics well, and that he 
must possess facility and readiness in the use 
of symbols. 
In the introduction, some of the fundamen- 
tal principles on which the science is based 
are discussed. One or two terms concerning 
which there has been more or less dispute are 
handled a little delicately in the beginning. 
An instance of this is the use of the word 
‘force.’ The author is a little shy about de- 
fining it at first. His confidence grows, how- 
ever, as the work progresses; and he once or 
twice hints at, but never quite reaches, the 
neat statement of Clerk Maxwell, that force 
is ‘ one of the aspects of a stress.’ 
A chapter is devoted to the processes of 
measuring space, time, and mass, in which the 
rather discouraging statement is made, that 
‘ood linear measurement, in whatever way 
effected, ought to present an error less than one- 
millionth of the whole.’’ There is a well-written 
chapter on work and energy, including a brief 
discussion of the indicator diagram. This is 
followed by the subject of kinematics, cover- 
ing more than a hundred pages. 
The treatment of this subject is somewhat 
novel for a book of this class, including, as it 
does, a tolerably complete discussion of simple 
harmonic motions, their composition and reso- 
lution ; astatement of Fourier’s theorem ; a dis- 
cussion of waves and wave-motions ; the prop- 
agation of waves, their reflection, refraction, 
interference, and diffraction; the vibrations of 
chords, membranes, etc. In the statement of 
Ptolemy’s law for reflection, and Fermat’s for 
refraction, often known as the principles of least 
distance and least time, the author has failed 
to note the very important exceptions to both, 
or to give the limitations to which they are 
subject. — 
There follows the subject of kinetics, in which 
some general propositions in reference to forces 
are derived from those already established in 
the study of motion. Moment of inertia, radius 
of gyration, and energy of a rotating body, are 
SCIENCE. 
633 
more thoroughly treated than is customary in 
such a treatise. 
There is a very satisfactory chapter on at- 
traction and potential. Potential of a point in 
space, equipotential surfaces, lines and tubes 
of force, etc., are discussed in a manner so 
clear and intelligible as to enable the student 
to be somewhat master of the situation when 
he comes to the practical application of these 
conceptions. The chapter on gravitation and 
the pendulum is satisfactory ; but, in the last 
proposition, the author has made the not uncom- 
mon mistake of failing to correctly state the 
conditions of the reversible pendulum. It isa 
little curious that it is not oftener observed that 
a symmetrical bar will oscillate about any two 
points equally distant from the centre of grav- 
ity in the same time. Students are likely to 
be considerably puzzled when they attempt to 
determine in this way the length of a single 
pendulum, and discover, that, the shorter the 
pendulum, the longer the period of vibra- 
tion. 
In many text-books the study of matter and 
its properties forms the subject of the opening 
chapter ; with some propriety, perhaps, as mat- 
ter is assumed to be the solid foundation upon 
which the science of physics rests. In this 
volume, however, it is not discussed until nearly 
two hundred pages have been passed over. 
One of the peculiar features of the treatment of 
the subject by our author is the admission of the 
ether as a form of matter; and the reasons for 
so doing are ably presented. Its properties as 
matter are explained as far as known or sur- 
mised, and the vortex atom is not forgotten. 
The chapter includes a discussion of the molec- 
ular constitution of matter, a brief considera- 
tion of surface-tension and superficial viscosity, 
with their application to capillary phenomena, 
and a brief study of viscosity of solids, liquids, 
and gases. 
The middle of the book is passed before the 
study of heat is begun. Heat is considered 
as including two totally distinct forms of en- 
ergy; and the treatment of what is known as 
radiant heat is deferred until a later period. 
Under the head of heat proper will be found 
some discussion of the principles of thermo- 
dynamics, including a treatment of Carnot’s 
cycle. It occupies forty pages, and might 
have been improved by a more complete pres- 
entation of the subject of conduction. Sound 
is considered through fifty pages, in which 
musical intervals and scales, the vibration of 
strings, and the propagation through solids, 
liquids, and gases, receive rather more atten- 
tion than is usual. 
