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POPULAR SCIENCE REVIEW. 
student procuring Webb’s “ Celestial Objects,” which is published by Mr. 
Hardwicke, as the best companion to the present work. Of course there 
are some few stars in Mr. Webb’s book not figuring here ; but there need 
be no difficulty about this, as Mr. Webb gives in every case the right ascen- 
sion and declination. We quite approve of Mr. Proctor’s plan of omitting 
the barbarous constellation figures ; it is the first step towards getting rid of 
them altogether, which we hope will soon follow. His instructions to 
beginners are ample, clear, and to the point, and we do not see why any 
boy of intelligence might not with the assistance of this atlas make the 
acquaintance of the heavens in a single winter. The maps, which are twelve 
in number, are admirably clear, and all contain stars as low as under the 
sixth magnitude. We approve, too, of the fact that each map contains a table 
of explanation of the abbreviations'; for though they are identical on each, 
it would have been extremely awkward to have to refer back from the 
third or fourth map to the first, had the other plan been followed. Mr. 
Proctor has some amusing remarks about literary authors’ ignorance of 
astronomy, Dickens appearing as an example ; whilst he declares that 
“ Tennyson is singularly accurate in all astronomical details.” In conclusion, 
we can only thank the author for a very good book, and wish it the success 
it so thoroughly merits. 
AN INDEX OF SPECTRA.* 
W E cannot predict that the author of this work will be rewarded com- 
mercially for the labour he has undertaken ; but most certainly he 
deserves the hearty thanks of scientific spectroscopists for the arduous task 
he has so well discharged, in making some effort to render the labours of 
those who are engaged in working with the spectroscope, something more 
systematic than they have been of late. Anyone who knows anything of 
this very difficult, and we may almost say novel method of research, is 
aware of the inconvenience arising from the employment of different scales 
in the mapping of spectra. Now the object of the author is to render 
spectroscopic research simple by collecting all existing measurements of the 
spectra of the elements, and presenting them on a uniform scale of wave- 
lengths. This scale, which is adapted to the measurements obtained from 
very large spectroscopes, is also as suitable for an instrument which has but 
a single prism. We hope, therefore, with Professor Roscoe, that this index 
of Dr. Watts may lead eventually to the adoption of an uniform scale. 
Some excellent plates accompany the volume. These give the spectra 
of sixty-one of the elements known to chemists ; the first plate is devoted 
to coloured double spectra of carbon, sulphur, and nitrogen ; those at the 
end of the work give the spectrum of each element, on Bunsen’s plan, viz. 
the intensity of each bright line being represented by the height of the line 
which corresponds to it. Altogether the book is a careful and well-done 
piece of work. 
* “ Index of Spectra.” By W. Marshall Watts, D.Sc., Senior Physical 
Science Master in the Manchester Grammar School. With a Preface by 
H. E. Roscoe, B.A., F.R.S. London : Gillman, 1872. 
