40 Analyses of Books. [January, 
entertained that it might be simply and rapidly effected by means 
of the spectroscope. The careful and prolonged researches of 
Prof. Chandler Roberts, F.R.S., Chemist to Her Majesty’s Mint, 
and of Mr. A. E. Outerbridge, Assistant in the United States 
Mint, prove that for the present these anticipations were un- 
founded. Mr. Capel has, indeed, proved that the i-4000th part 
of a milligramme of gold will show its characteristic speCtrum if 
the spark is passed through the weak solution of the pure metal. 
But on operating on an alloy containing 3*8 per cent of gold, the 
remainder being silver and copper, the speCtra of the two latter 
metals were alone visible. An alloy of copper with from 20 to 
25 per cent of gold was tried, and even here the gold speCtrum 
was barely visible. Yet if gold is alloyed with even 1 per cent 
of copper the speCtrum of the baser metal is perfectly distinCt. 
In an alloy of copper with even 20 per cent of nickel the latter 
cannot be distinguished by the spectroscope. Hence the above- 
mentioned authorities both conclude that when two or more 
metals are jointly present the spark can, to some extent, eleCt as 
its medium or vehicle the one which is most readily volatilised, 
Hence extreme sensibility is not a universal characteristic of the 
speCtrum reactions. 
There is another practical difficulty not readily to be overcome. 
The alloys of gold used in the arts are not, and cannot be made, 
absolutely homogeneous. Two portions, each of 10, or 5, or 
2 grains, might give results exactly corresponding ; but the mi- 
nute particles of metal which are volatilised, and which give the 
result in speCtroscopic analysis, cannot be assumed to be safe 
representatives of the entire ingot. 
The work before us has, in the general opinion of practical 
men, no rival in English literature, and we have every confidence 
that the present edition will be welcomed as an improvement on 
the foregoing. 
The Herring and the Herring Fishery , with Chapters on Fishes 
and Fishing , and our Sea Fisheries in the Future. By J- 
W. De Caux. London : Hamilton, Adams, and Co. 
This little book contains such a diversity of matter that the most 
varied tastes may be gratified by its perusal. As regards the 
portion which more particularly appeals to our attention, the 
author almost at the outset exposes an erroneous classification of 
fishes of which some naturalists are guilty, i.e ., a division into 
such as live at the bottom of the sea, such as invariably live in 
mid-water, and such as invariably live at or near the surface. 
He denies the existence of the surface swimmers as a class. 
The herring and mackerel, types of this group, are oftener 
