REVIEWS. 
75 
UNITS AND PHYSICAL CONSTANTS * 
T HIS "book/ says the compiler in his preface, 1 is substantially a new 
edition of my Illustrations of the C. G. S. System of Units, published 
in 1875 by the Physical Society of London, supplemented by an extensive 
collection of physical data. The title has been changed with the view of 
rendering it more generally intelligible. Though the publication is no longer 
officially connected with the Physical Society, the present enlarged edition 
is issued with the Society’s full consent and approval.’ In the first issue it 
was stated that its main object was to facilitate the quantitative study of 
Physics, and especially of the relations between its different branches. 
One uniform scale, a luxury hitherto unknown to the scientific calculator, is 
thus for the first time presented to the observer. The work is divided into 
eleven chapters, the first two of which deal with the general theory of Units, 
and the choice of three representing Mass, Length, and Time respectively. 
These are then applied to Mechanics, to Hydrostatics, to Strain, Stress, and 
Resilience, a new term introduced to remedy the ambiguity of 1 Elasticity,’ 
to Astronomy, to the velocity of Sound and of Light, to Heat, Magnetism, 
and Electricity. An appendix contains the Reports of the Royal Association 
Committee on Dynamical and Electrical Units, of which Professor Everitt 
w as reporter. 
The question of uniformity and the particular fitness for the purpose of 
the units chosen are too large for discussion in a mere notice of the book ; 
but, granting its premises, there can be no doubt that the work has been 
thoroughly and judiciously carried out. W. H. Stone. 
MODERN CHROMATIC S.f 
T HE author of this very interesting work states his object to be to present, 
in a clear, logical, and, if possible, attractive form, the fundamental 
facts connected with our perception of colour, so far as they are at present 
known, or as they concern the general and artistic reader. For the explana- 
tion of these facts, the theory of Thomas Young, as modified and set forth by 
Helmholtz and Maxwell, has been consistently adhered to. It has also been 
his endeavour to present in a simple and comprehensible manner the under- 
lying facts upon which the artistic use of colour necessarily depends. The 
book commences with a general statement as to the Transmission and Reflec- 
tion of Light, in which it is shown that as painted or stained glass transmits 
enormously more fight than pigments reflect in a properly lighted room, it 
follows that the worker on glass has at his disposal a much more extensive 
* Units and Physical Constants. By J. D. Everitt, F.R.S., &c., Professor 
of Natural Philosophy in Queen’s College, Belfast. London: Macmillan. 
Crown 8vo, pp. 175. 
t Modern Chromatics, with Applications to Arts and Industry. By Ogden 
N. Rood, Professor of Physics in Columbia College. 8vo. pp. 530, with 130 
Illustrations. London : "C. Kegan Paul & Co. (International Scientific 
Series.) 
