REVIEWS. 87 
gather any additional detailed information respecting the various processes to 
which they may have occasion to refer. 
We cannot turn over the pages of the historical sketch which forms the 
opening chapter of the book, without experiencing a feeling of satisfaction 
at the manifestly large share taken by our countrymen in the development of 
this branch of industrial science. Next we have an exposition of the princi- 
ples and laws of “ Electro-Metallurgy ” which is for the most part all that 
could be desired. The atomic weights of elementary substances, as given in 
this chapter, vary considerably in some cases from those at present accepted. 
When speaking of the means of measuring a galvanic current, the author 
states that “ the instruments usually employed for that purpose are either a 
galvanometer or a voltameter,” and further, that “ what is termed ‘ a tangent’ 
one may be conveniently employed.” The reader will hardly gather from 
this that the two forms of galvanometer differ very materially as regards their 
use as ?neasurers of currents. What is generally known, is that in the instru- 
ment usually termed the galvanometer (or multiplier), the deflections of the 
needle, while increasing with the intensity of the current, bear no simple 
relation to it, and the relation has to be determined experimentally for each 
apparatus ; in the case of the tangent compass, however, the tangents of the 
angles to which the needle is deflected by the currents are proportional to 
the currents causing the deflections. From the theoretical we pass to the 
practical division of the book, which occupies about one half of the volume, 
and is devoted to the processes employed for the electro-deposition of metals 
| and metalloids. Glass I. is intituled “ Gaseous Metals,” and they are hydrogen. 
I Although hydrogenium is referred to, and Bottger’s modification of an earlier 
experiment is described, the name of Graham is conspicuous by its absence ; 
the author directs attention to his own researches on the electrolysis of 
hydrofluoric acid and hydrochloric acid. He speaks in this chapter of 
water as a “ salt ” of hydrogen (p. 94) ; then we find “arsenic acid” is a “ salt ” 
(p. 97), black oxide of manganese is a “ salt ” (p. 250), and caustic lime is 
a “ salt ” (p. 292). What, we ask in despair, is not a “ salt ” P Mr. Gore appears 
to have lost sight of the chief aim of the series of text-books of which his forms 
one ; they are intended to serve for the use of practical men, and as regards 
style and subject-matter to be within the comprehension of working men, and 
suited to their wants. Our chemical nomenclature is unhappily difficult and 
bewildering enough as it is, and every effort should be made to simplify it 
and render it comprehensible to every reader. Will those who use his book 
know that by “ chloride of ammonia,” “ chloride of ammonium ” and “ sal 
ammoniac ” three names used within a few pages of each other, it is intended 
to indicate the same substance ? Again, on one page we are told that “ (iron) 
protosulphate” is also called “ green vitriol”; in the next paragraph we read 
of “ferrous sulphate ”; in the next ot' “ protosulphate (green copperas) ” ; in 
the next but one of “ ferrous sulphate (green vitriol) ” ; and again, in the same 
paragraph, of “ sulphate of iron.” In ringing the changes which are possible 
with the names of this substance the author has in this short space hardly 
omitted one. The article on the electro- deposition of silver is very lull and 
very useful. The quantity of silver used in plating wares which are sent in such 
large quantities to the colonies is stated to be about one ounce to the square 
mile ! In Birmingham iron snuffers are sometimes “ silvered ” wholesale at 
