THE YOUNG SCIENTIST. 
103 
reported that a paper at Turin called Light, is 
to appear shortly printed in ink, which will be 
luminous when darkness sets in. Who can say, 
indeed, that a policeman when smeared in this 
luminous composition, will not be sometimes 
visible on his beat at night ? " 
Blacking for Leathei. 
The following- has been used for harness, and 
also for leather bags, boots, etc., and is said to 
be admirable, if carefully prepared : Ext. log- 
wood, 2 oz. ; potass, bichrom, 2 drachms ; yellow 
pruss. potass., 2 drachms ; powdered borax, 3 oz. ; 
liq. ammonia, 2 oz. ; shellac, 16 oz. ; water, 1 gal- 
lon. Dissolve the extract in the water, heating 
the liquid to nearly boiling, then add the chrom- 
ate and tlie prussiate of potash. After a deep rich 
blue color has developed, add the borax, and 
when it has dissolved add the shellac, and lastly 
the ammonia ; keep the whole at a gentle heat, 
stirring until the smell of ammonia has gone. 
The solution of logwood must be heated nearly 
to the boiling point before the salts of potash 
are added, or only a dirty blue color will be 
obtained. 
• o • 
Iridescent Copper. 
A new invention for coating iron and steel 
Yv'ith iridescent copper, has been devised by Dr. 
Weil, of Paris, and is thus described in the 
Revue Potytechnique. First, thirty-five parts 
of crystallized sulphate, or an equivalent 
amount of any other salt of copper, are precipi- 
tated as hydrated 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 is to be added, w^hen a clear solu- 
tion of copper will be formed. 
The object to be coppered is to be cleaned with 
a scratch brush in an alkaline bath containing 
organic matter, such as solution of malt, etc. 
It is then attached as a cathode, immersed in 
the coppering bath, and treated with the usual 
precautions, when it will become coated with an 
adherent film of metallic copper. 
As the bath graduallj^ loses its copper, oxide 
of copper, 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 notably 
exceeds this proportion, certain metallic colors 
are produced on the surface of the object. These 
effects may be employed for ornamental and 
artistic purposes. 
According to the time of the immersion, the 
j strength of the current, and the proportion of 
j copper to the tartaric acid, the iridescences may 
j be produced of different shades and tints, which 
j may be varied or intermingled by shielding 
certain parts of the object by an impermeable 
coating of paraffine or varnish, while the irid- 
escent effect is being produced on the parts 
left exposed. All colors, from that of brass to 
bronze, scarlet, blue, and green, may thus be 
produced at will. 
Oil on Woodwork,— Carefully-conducted ex- 
periments have demonstrated the fact that sea- 
soned wood, well saturated with oil when put 
together, will not shrink in the dryest weather. 
Wheels have been known to run many years, 
even to wearing out the tires. Very many dollars 
might be saved annually if this practice was 
adopted. Boiled linseed oil is the best for general 
use, although it is now kaown that crude petro- 
leum on even old wheels is of great benefit. 
To Repel Mosquitoes.— Mr. Ivers W. Adams 
writes from Batlmrst, N. B., to Forest and Stream, 
that he tried a dozen prescriptions for repelling 
mosquitoes, flies, and similar pests, and found 
none of them effective until he came across the 
following, which are dead sure every time: 
" Three oz. sweet oil, l oz. carbolic acid. Let it 
be thoroughly applied upon, hands, face, and all 
exposed parts (carefully avoiding the eyes) once 
every half hour, when the flies are troublesome, 
or for the first two or three days, until the skin is 
filled with it, and after this its application will be 
necessary only occasionally. Another recipe, 
equally efficacious, is: Six parts sweet oil, one 
part creosote, one part pennyroyal. Either of 
these is agreeable to use, and in no way injurious 
to the skin. We have both of these in our camp 
with us, and all flies keepia safe distance." 
Paste.— A correspondent of New Remedies giye& 
the following recipe for a paste for use in pre- 
scription books and labels: 
" I dissolve half an ounce of alum in a pint of 
boiling water ; to this I add an equal weight of 
flour, made smooth in a little cold water, and a 
few drops of oil of cloves, letting the whole come 
to a boil. This paste will keep months. I put it 
in glass, or ordinary ointment jars. This paste 
is handy, too, for domestic purposes. My children 
have many toys that come in wooden boxes, but 
these will break at the corners and soon come to 
pieces, When a box begins to give out. I take a 
piece of cambric or calico, and with the brush and 
paste cover the box so that it will bear constant 
usage for months. Then, if the cover gives out, 
I pull it off and put on another one. Again, a 
doll's arm or leg comes off; but a piece of muslin 
and a bit of paste restores the article, so that it is 
as good as it was before." 
