56 THE YOUNG 
cysts or capsules in which the *' worms" are 
lodged may readily be detected with the 
naked eye, and a power of twenty diameters 
shows the worms themselves very plainly. 
The only way to avoid these creatures is to 
thoroughly cook any meat that may be 
eaten — especially pork or ham. Trichina 
are, however, sometimes found in beef, the 
cattle having been fed on grass manured 
with matter from slaughter-houses, and the 
pig pens attached thereto. In these slaugh- 
ter-houses the rat is the greatest distributor 
of trichina. Rats are almost sure to get 
trichina from some of the flesh that they 
eat; while sick and feeble from the effects 
of this diet, they are apt to be caught by 
the pigs, in whom the trichina then multi- 
ply enormously. The extent to which rats 
and mice are infected with trichina leads to 
the further fact that most cats are so in- 
fected. We have in our possession several 
preparations made from diflFerent parts of 
the cat, and the muscles are all infected 
with trichina. 
How to Solder. 
There are two ways in which this operation 
may be performed; one is by using the ordi- 
nary soldering iron ; in the other the heat is 
obtained from a lamp. The first is the most 
workmanlike, and gives the best results, but 
the latter is most easily learned, and as any of 
our readers can easily manage to join pieces of 
brass, copper, tin plate, iron, etc., in this way, 
we will describe it first. 
In soldering, the essential conditions are 
that the surfaces to be united shall be clean, 
and that they shall readily unite with the metal 
used for solder. All surfaces should therefore 
be scraped bright with an old knife, a file, a 
scraper, or even emery paper, but as they will 
not stay bright when heated, we must use 
something which will keep them so. For cop- 
per, brass or tin plate, resin is very good, but 
for other metals a solution of zinc in hydro- 
chloric acid is best. Fill a small phial half full 
of dilute hydrochloric acid, put into it as much 
zinc as it will dissolve, and you have the sol- 
SCIENTIST. 
dering fluid, or liquid solder, which is now so 
much advertised, and which is sold on the 
sidewalks in New York. 
The ease with which the different metals may 
be soldered is in order as follows : Tin plate, 
copper, platinum, silver, brass, wrought iron, 
steel, cast iron. We have heard some tin- 
smiths say that cast iron cannot be soldered, 
but this is a mist ike; we have done it often. 
The bright metal generally used for solder is 
an alloy of tin and lead — two parts of the for- 
mer to one of the latter. A more fusible solder 
is sold in small strips at the hardware stores. 
A little bit of solder may, however, be obtained 
from any tinsmith, and will serve every pur- 
pose. Where solder cannot be had conveni- 
ently, tin foil, such as comes round tobacco, 
answers well. We have done a great deal of 
work with it. This tin foil is not pure tin, but 
consists of a sheet of lead between two sheets 
of tin, the compound sheet being rolled out 
thin. 
For a lamp, anything will do. We have used 
candles and kerosene lamps, but greatly prefer 
a spirit lamp, as it is free from smoke and 
grease. An old ink bottle (one of the little 
triangular ones), with a hole through the cork, 
and through the hole a tube for the wick, does 
well. 
Having procured the materials, let us now 
proceed to work. Suppose the job is to fasten 
a wire to a tin can for a battery. Scrape the 
end of the wire bright, and also scrape the tin; 
lay some solder on the latter; touch with a 
drop of soldering liquid, and heat over the 
lamp till the solder melts. The heat should 
be applied only to the spot where the solder 
rests. Dip the end of the wire in the solder- 
ing liquid, and as soon as the solder melts 
place the wire where it is to go, and hold it 
there till the solder has flowed all round it. 
Eemove it from the flame and allow it to cool. 
It will be very firmly fastened. 
Suppose we wish to join two wires together. 
Hammer the ends flat, file them bright, lay 
them together, and bind firmly with fine iron, 
brass, or copper wire. Moisten with soldering 
liquid, lay a piece of solder on the joint, and 
heat in the lamp. When cold the joint will be 
very strong. By making a long splice, and 
filing off the binding wire after the solder has 
cooled, a joint may be made which will be 
scarcely perceptible, and yet be very strong. 
