THE YOUNG SCIENTIST. 
BOOK NOTICES. 
Practical Microscopy. Bv George E. Davis, 
F.R.M.S., i^M.C, F.C.S. Illustrated with 257 
AVoodcuts and a Coloi'ed Frontispiece. Price, 
*3.00. For sale by Industrial Publication Co., 
U Dey street, New York. 
This work has just been issued in London, and 
forms a handsome small 8vo. of 335 pages. The 
author states that his " object in presenting this 
work to the student of microscopy is to supply, 
at a reasonable cost, a book written upon some- 
what similar lines to Quekett's ' Practical Trea- 
tise on the Use of the Microscope,' the second 
and last edition of which appeared in 1852." Un- 
fortunately for the author's accuracy of state- 
ment, the second edition of Quekett's work was 
not the last. The third, with considerable im- 
provements, appeared in 1855. It is evident, there- 
fore, that Mr. Davis has not made a very careful 
study of his proposed model. This, however, is 
a matter of trifling consequence, as it would 
hardly be worth while at this day to follow Que- 
kett's work closely as a model. 
That there is an urgent demand for a thorough 
work on the use of the microscope and the prepa- 
ration and mounting of objects, is pretty gener- 
ally felt. We hardly think, however, that the 
in-esent volume quite realizes the necessary con- 
ditions, for, although three times the price, it 
really does not contain more matter than some 
dollar books now in market— the type being large 
and the lines double-leaded. Besides this, the 
work is largely made up of extracts from peri- 
odicals and catalogues (not always acknowl- 
edged), and there is a want of accuracy which is 
to be regretted. Thus, Tolles' address is still 
Canastota, instead of Boston ; the vertical illumi- 
nator of Prof. H. L. Smith is credited to Powell & 
Lealand, and Beck ; the searcher for diatoms is di- 
rected to examine the stomachs of "flsh, especi- 
ally crustaceans and molluscs ;" and the student 
is cautioned against attempting to make prepar- 
ations of skin, tongue, liver, lung, etc., until he 
has become a moderately expert experimental- 
ist—advice which bears almost too great a resem- 
blance to the old lady's caution not to go near the 
Avater until the art of swimming had been learnt. 
We are glad to see that the author has carefully 
read "How to Use the Microscope," as several 
unacknowledged passages and figures show. 
But notwithstanding the somewhat unsatisfac- 
tory nature of the book, it contains enough mat- 
ter, which can only be otherwise found in scat- 
tered form, to make it a welcome addition to the 
libraries of most microscopists. 
Cleaning> Eng^ravings. 
The following? directions for cleaning engrav- 
ings we find in several exchanges, all claiming 
it as original : If brown spots and rings of mil- 
dew liave not made their appearance, float the 
engraving face downward for 24 hours on a 
large quantity of water, in a vessel perfectly 
free from grease and soil of all kinds. Lift it ; 
from the vrater on a perfectly clean sheet of \ 
glass, drain, transfer to blotting paper without \ 
touching it, then transfer to fresh blotting paper, ! 
drj^, rub with bread, as is done in drawings, and ') 
iron. If the stains are bad, or are not removed i 
by this plan, place the engravings in a shallow^ 
dish, and pour water over them until perfectly 
soaked. Carefully pour off the water and re- 
place it with a solution of chloride of lime (1 
part liq. calcis chlorate to 39 parts water). As 
a rule the stains disappear as if by magic. It 
not, pour on the spot pure liq. calcis chlorate ; 
if that does not succeed, add a little acid nitro- 
hydro-chlor. dil. As soon as the stain disap- 
peais, wash the engraving carefully with suc- 
cessive portions of water until all the chlorine is 
removed. Then steep it in a weak solution of 
glue and gelatine, which may be colored with 
coffee grounds, to give the engraving a yellow 
color. Then dry between blotting paper, under 
a weight, and iron, with a sheet of clean paper 
between the iron and the print. Small grease 
spots may be removed by putting powdered 
French chalk over them, a piece of clean blot- 
ting paper over the chalk, and a hot iron over 
that. If the stains are larger, benzine must be 
used, applying it in a circle around the stain be- 
fore touching the stain itself. 
Iridescent Copper. 
A new invention for coating iron and steel 
with iridescent copper, says the Revue Polytech- 
nique, is the work of Dr. Weil, of Paris. First, 
35 parts of crystallized sulphate, or an equiva- 
lent amount of any other salt of copper, are pre- 
cipitated as by d rated oxide, by means of caustic 
soda or some other suitable alkaline base ; this 
oxide of copper is to be added to a solution of 
150 parts of Eochelle salts, and dissolved in 1,000 
parts of water ; to this 60 parts of best caustic 
soda, containing about 70 per cent. NaO, is to be 
added, when a clear solution of copper will be 
formed. The object to be coppered is to be 
cleaned with a scratch-brush in an alkalino-or- 
ganic ba,th, attached as a cathode, immersed in 
the coppering bath, and treated with the usual 
precautions, when it will become rapidly coated 
with an adherent film of metallic copper. As 
the bath gradully loses its copper, oxide of cop- 
per, as above prepared, should be added, to 
maintain it in a condition of activity, but the 
quantity of copper introduced should not ordin- 
arily exceed that above prescribed, as compared 
with the quantity of tartaric acid the bath may 
contain. If the quantity of copper notablj'' ex- 
ceeds this proportion, certain metallic irisations 
are produc jd on the surface of the object. These 
effects may be employed for ornamental and 
