408 
Notices of Books „ 
rjuly, 
The present work may be said to be in some sort the comple- 
ment of Mr. Lockyer’s former work on “ The Spectroscope and 
its Variations,” seeing that it goes much more deeply into the 
theoretical part of this subject. The subject of wave-motion 
having been explained, the author next describes the principal 
methods of demonstrating spectral phenomena, and the value 
and use of the photographic camera in their registration. 
The fourth chapter, in which atoms and molecules are treated 
of in relation to the specftroscope, contains a large amount of 
theoretical speculation of a very interesting character; and the 
same may be said of the chapter on Dissociation, in which Mr. 
Lockyer boldly attacks the integrity of certain of the elements, 
such as calcium and hydrogen. Mr. Lockyer’s speculations in 
this direction are of a most suggestive kind, and ought to form 
the starting-points for a large amount of investigation. If our 
present elements are ever to be split up, either theoretically or 
practically, the specftroscope will have undoubtedly commenced 
the work. 
The account given of Messrs. Lockyer and Roberts’s experi- 
ments on the quantitative analysis of gold and other alloys show 
that one of these days the specftroscope will play an important 
part in the assay of the precious metals. The results given by 
these experiments are of a very promising nature, and it is only 
the close attention which Mr. Lockyer has to give to the more 
important branches of Specftroscopy that prevents him and his 
colleague from bringing their researches to a thoroughly practical 
termination. By the present method an assay takes at least two 
hours, whereas by the use of the specftroscope it might be per- 
formed in a few minutes. 
The book is well illustrated by eight photo-lithographic plates 
of specftra and fifty well-executed woodcuts. 
Industrial Chemistry . A Manual for Use in Technical Colleges 
and Schools, and for Manufacturers, &c. Based upon a 
Translation, partly by Dr. T. D. Barry, of Stohmann and 
Engler’s German Edition of Payen’s “ Precis de Chimie 
Xndustrielle.” Edited throughout, and supplemented with 
Chapters on the Chemistry of the Metals, &c., by B. H. 
Paul, Ph.D. Illustrated with 668 Engravings on Wood. 
London : Longmans and Co. 1878. 
After a very attentive examination of this, the most recent 
contribution to the literature of Industrial Chemistry, we must 
confess that we are utterly puzzled to discover for whose benefit 
this book has been compiled. Judging from the title-page and 
preface, it is not only intended for manufacturers and technolo- 
