THE YOUNG SCIENTIST. 
63 
I How to Kill Entomolog-ical Specimens.— 
' A correspondent says the method of killing ento- 
i mological specimens, by putting them in a glass 
cylinder closed at one end, and then inserting a 
wad of tow saturated with ether on closing the 
other end of the cylinder, is very good ; but when 
putting the insect, especially butterflies, in the 
tube, it flutters its wings, and so loosens some of 
the colors. A better way is to put a small bit of 
chloroform on the insect's head as soon as it is 
caught, and the effect is that it instantaneously 
dies! not even a relaxation of the muscles being 
perceptible. 
Liquid Slating" for Blackboards.— Alcohol, 
<95 per cent)., i pints ; shellac, 8 ounces ; lamp- 
black, 12 drachms ; ultramarine blue, 20 drachms ; 
powdered rotten stone, 4 ounces ; powdered pum- 
ice stone, 6 ounces. First dissolve the shellac in 
the alcohol, then add the other ingredients, finely 
powdered, and shake well. To apply the slating, 
have the surface of the board smooth and per- 
fectly free from grease. Shake Avell the bottle 
containing the preparation, pour out a small 
<iuantity only on a dish, and apply it with a new 
flat varnish brush as rapidly as possible. Keep 
the bottle well corked, and shake it up every time 
before pouring out the liauid. 
Depositing" Brass by Electricity.— Herr 
Hess, in the Metallarheiter, gives the following 
directions for this process: The first step is to 
thoroughly cleanse the articles, either by means 
of emery, or by laying them overnight in a weak 
bath of sulphuric acid. They are then washed 
off with water, a weak soda solution, and then 
immersed as the cathode of a bath consisting of 
1i}4 parts of sulphate of copper, 20 parts sulphate 
of zinc, and 45 parts cyanide of potassium, in 300 
parts of water. The anode should be two plates 
of zinc and copper of equal size. The color of 
the resulting brass coating may be modified by 
varying the depth of immersion of one or the 
other of the plates. The galvanic current should 
be a strong one, and tlie liberation of hydrogen 
bubbles on the object to be brassed should be 
plentiful. It is important, however, to note that 
the objects should be first coppered to insure a 
strong attachment of the brass coating. 
Stimulating Progress among Young Me- 
chanics.— Honorable competition in actual work 
is a great incitement to progress. This, we 
think, is well applied by an English society 
of turners. The subjects of competition were: 
turning in ivory, pottery, stone and jet; and 
steel, brass and gold for horological purposes. 
The competition in ivory included vegetable 
ivory. The Qualities considered in awarding the 
prizes were: Beauty of design, symmetry of 
shape, utility, and general excellence of work- 
manship ; exact copying, so that two objects pro- 
duced should be fac similes in every part, or ex- 
act measures of capacity: fitness of the work or 
design for the purpose proposed ; ability to turn, 
whether circular or oval ; and novelty in applica- 
tion of turning or in design. Carving was ad- 
missable, but it was to be subsidiary to the turn- 
ing. The candidate was to make his own selec- 
tion from the above conditions ; but the one who 
best fulfilled the largest number, including the 
most important qualities, was preferred. The 
work to be all hand-turning, produced in the 
lathe, without special rest or tool apparatus, and 
the carving to be the work of the exhibitor. 
Fitting Grlass Stoppers.— Very few stoppers 
fit properly the bottles for which they are in- 
tended. The stoppers and bottles are ground 
with copper cones, fed with sand and made to 
revolve rapidly in a lathe, and the common stock 
are not specially fitted. To fit a stopper to a bot- 
tle that has not been ground, use emery or coarse 
sand kept constantly wet with water, and re- 
placed with fresh as fast as it is reduced to pow- 
der. When all the surface has become equally 
rough, it is considered a sign that the glass has 
been ground to the proper shape, as until that 
time the projecting parts only show traces of 
erosion. This is the longest and hardest part of 
the work, as after that the glass simply needs fin- 
ishing and polishing. For that purpose emery 
only can be used, owing to the fact that the ma- 
terial can be obtained of any degree of fineness, 
in this respect differing from sand. Otherwise 
the operation is the same as before, the emery 
being always kept moistened, and replaced when 
worn out. The grinding is continued until both 
the neck of the bottle and the stopper acquire a 
uniform finish, of a moderate degree of smooth- 
ness, and until the stopper fits so accurately that 
no shake can be felt in it, even though it be not 
twisted in tightly. 
Uranine.— This is the most recently discov- 
ered, and perhaps the most remarkable, of all the 
coal tar or aniline group of coloring substances, 
now so extensively used for the adornment of the 
finest fabrics. Uranine is said, by chemists, to be 
the most highly fiuorescent body known to sci- 
ence. Its coloring power is astonishing ; a single 
grain will impart a marked color to nearly five 
hundred gallons of water. 
A most interesting experiment, which anybody 
may try, consists in sprinkling a few atoms of 
uranine up on the surface of water in a glass 
tumbler. Each atom immediately sends down 
through the water what appears to be a bright 
green rootlet, and the tumbler soon looks as if it 
were crowded full of beautiful plants. The root- 
lets now begin to enlarge, spread and combine, 
until we have a mass of soft green-colored liquid. 
Viewed by transmitted light, the color changes to 
a bright golden or amber hue ; while a combina- 
tion of green and gold will be realized, according 
to the position in which the glass is held. For 
day or evening experiment, nothing can be pret- 
tier than these trials of uranine, which are es- 
pecially entertaining for the young folks. We 
are indebted for examples of the color to the edi- 
tors of the Soientiflc American, who are send- 
ing out specimens, free of charge, to all their 
readers. 
