THE YOUNG SCIENTIST. 
50 
meet in the box and combine, forming a 
dense white vaj^or. Wlien the paper or 
membrane covering the end of the box is 
tapped smartly with the finger, the air 
and vapor rush out of the hole at the op- 
posite end, and form magnificent white 
SMOKE EINGS. 
rings, which travel quite a distance, ex- 
panding and curling in a most beautiful 
manner. The experiment is one that is 
easily carried out, and it never fails to 
please. The arrangement we have figured 
is one that is well adapted to the lecture 
room. 
Bird Paste. 
Bechstein, a celebrated German ornitliolog-ist 
of the past g-eneratioii, recommends the follow- 
ing- pastes, both of which soon become sour, b.ut 
the formula can be easily modified so that the 
food could be kept as a dry powder, which would 
not alter : 
No. 1. Take a stale well-baked white loaf, soak 
it thoroughly in fresh water, squeeze out the 
water, and pour boiled milk over it, adding 
about two-thirds of well-sifted barley or wheat 
meal. 
No. 2. Grate a carrot very finely, soak a small 
white loaf in water, squeeze it out, and put it 
with the carrot in an earthen pan, add two 
handt'uls of barley or wheat meal, and mix 
thoroughly: 
" The first paste," says Bechstein, " agrees so 
well with all my birds, that they are always 
healthy and preserve their feathers, so that 
they have no appearance of being- prisoners. 
Sometimes, as a delicacy, they are g:iven ants' 
eggs, or a few meal worms." 
Mr. Sweet recommends the following : Hemp 
seed crushed very small, in boiling- water, is 
mixed thoroughly with an equal quantity of 
bread soaked and squeezed dry, and an equal 
quantity of lean raw meat minced fine. Another 
authority says that, for the lark, barley meal, ' 
with cabbage, chopped cress and poppy seed, \ 
mixed with bread crumbs, or in winter with 
oats, forms a good food.— Chemist and Druggist. 
Plating and Gilding Without a Battery. 
A very useful solution of silver or gold for 
plating or gilding without the aid of a battery, 
may be made as follows : Take, say, one ounce 
of nitrate of silver, dissolved in one quart of dis- 
tilled or rain water. When thoroughly dis^- j 
solved, throw in a few crystals of hyposulphite I 
of soda, which will at first form a brown pre- 
cipitate, but which eventually becomes redis- 
solved, if sufficient hy]3osulphite has been em- I 
ployed. A slight excess of this salt must, how- 
ever, be added. The solution thus formed may 
be used for coating- small articles of steel, brass, l 
or German silver, or by simply dipping- a sponge 
in the solution and rubbing- it over the surface I 
of the article to be coated. I have succeeded in 
coating- steel very satisfactorily by this means, 
and have found the silver so firmly attached to I 
the steel (when the solution has been carefully | 
made) that it has been removed with consider- ! 
al)le difficulty. A solution of g-old may be made j 
in the same way, and applied as described. A 
concentrated solution of either gold or silver I 
thus made, may be used for coating parts of | 
articles which have stripped or blistered, by ap- \ 
plying it with a camel-hair pencil to the part, i 
and touching the spot at the same time with a ; 
thin clean strip (^f zinc. — Exchange. 
Preservation of Wood. 
In speaking of the well-known methods of 
preserving posts and wood which are partially 
embedded in the earth, by charring and coating 
with tar, it is said these methods are only effec- 
tive when both are applied. Should the posts 
be charred only, without the subsequent treat- 
n'lent with tar, the charcoal formation on the i 
surface w^ould only act as an absorber of the |i 
moisture, and, if anything, only hasten the j 
decay. By applying a coating of tar without j 
previously charring, the tar would only form a i 
casing about the wood, nor would it penetrate \\ 
to the depth which the absorbing properties of ! 
the charcoal surface would insure. Wood that 
is exposed to the action of water, or let into the 
ground, should first be charred, and then, while 
still hot, be treated with tar till the wood is i 
thoroughly impregnated. The acids and oils ! 
contained in the tar are evaporated by the heat, ^ 
and only the resin left behind, which penetrates i 
the pores of the wood and forms an air-tight 
and Avater-proof envelope. It is important to j 
impregnate the poles a little above the line of :j 
exposure, for here it is that the action of decay 
