102 Notices of Books. (January, 
results—above all things avoiding that question which ignorance 
so often addresses to genius, ‘ What is the use of your work ?” 
Let him make truth his object, however unpractical for the 
time being, that truth may appear. If you cast your bread thus 
upon the waters, then be assured it will return to you, though 
it may be after many days.” 
We trust our American cousins, or, as we should prefer to call 
them ‘brothers, speaking the same dear mother tongue,” will 
lay all this to heart, and let it bear good fruit. We rejoice to 
know that one of our own scientific men has been received by 
the Americans, as Dr. Tyndall has been received, and we trust 
that the establishment of these social relationships will do 
much to bind together the two great countries into still closer 
union. 
The Spectroscope and its Applications. By J. Norman Lockyer, 
F.R.S. Macmillan and Co. London: 1873. 8vo., 117 pp. 
Illustrated. 
Tuis is the first volume of a series of popular works on Science, 
to be called the Nature Series, because the subject-matter is first 
printed in ‘‘ Nature.’ Eight of these books are already announced, 
and some two or three will no doubt be ready by next October. 
The design is good, and the books will probably supply a want 
which is being felt in this country and America. Judging from 
the present volume, the series will resemble Messrs. Hachette’s 
Librarie des Merveilles more closely than any other works in our 
language. The general appearance, as to externals, is altogether 
prepossessing—the book is well printed on thick paper, profusely 
illustrated, and very neatly bound. 
The present volume consists of three lectures on the Spectro- 
scope, delivered before the Society of Arts in 1869. They here 
appear in a revived and somewhat expanded form, and the subject 
has, as far as possible, been brought up to the day of issue. 
The first lecture regards the matter from an historical and 
descriptive point of view. The broad points of interest con- 
nected with the history of the spectroscope are clearly discussed. 
The proof that lights which differ in colour differ in refrangi- 
bility; that the light of the sun consists of rays possesssing 
different refrangibilities ; the decomposition and recomposition 
of light. Newton, in his experiments, had used a round hole in 
a shutter for the admission of a beam of light ; while Wollaston, 
in 1802, made what our author calls ‘‘a tremendous step in 
advance,” by substituting a slit instead of a circular hole. This 
simple modification of Newton’s experiment permitted a spectrum 
of considerable purity to be obtained for the colours, instead of 
overlapping, were now seen more distinctly side by side, and 
with only their edges overlapping. In this spectrum Wollaston 
found breaks of continuity, not observed by Newton; he dis- 
covered the black lines at right angles to the length of the 
