THE YOUNG SCIENTIST. 
95 
of a pliant pole and teu feet of line, and his 
plunges, twistings, and straight-away dashes 
are more perplexing to the angler than the 
leaps, surges, and sulkings of the gamy trout 
or bass. The rat is generally landed, after sea- 
sonable sport, and killed by a blow from a 
bludgeon. 
In this connection we may state that thous- 
ands of small hooks are bought by sugar re- 
finers for ratting purposes. The hooks are 
baited with small pieces of beef on each, and 
then distributed about the building. The rats 
swallow beef and hook— the first is digested, 
the latter is not— death of course results. The 
remedy is said to be infallible. 
Notes on Belting. 
In putting on a belt be sure that the joints 
run with the pulleys, and not against them. 
Leather belts should be well protected against 
water, and even loose steam or other moisture. 
To obtain a greater amount of power from 
belts, the pulleys may be covered with leather ; 
this will allow the belts to run very slack, and 
give 25 per cent, more durability. In punching 
a belt for lacing, it is desirable to use an oval 
punch, the larger diameter of the punch being 
parallel with the belt, so as to cut out as little 
of the effective section of the leather as possi- 
ble. Begin to lace in the centre of the belt, and 
take care to keep the ends exactly in line, and 
to lace both sides with equal tightness; the 
lacing should not be crossed on the side of the 
belt that runs next the pulley ; thin but strong 
laces only should be used. A careful workman 
will see that his belts are redressed about every 
four months, by sponging the dirt from them 
with warm soap and water, then drying with a 
cloth, and, while still damp, rubbing in castor 
oil or currier's grease, which will be readily ab- 
sorbed, the leather being moist from washing. 
Castor oil has the additional advantage of pre- 
venting rats attacking the leather. 

J3ractical ^ints. 
American Silk Culture.— The Women's Silk 
Culture Association has given notice of its will- 
ingness to purchase cocoons from all parts of the 
country. Many persons in the South and West 
have raised cocoons, but have been unable 
hitherto to find a market for their product. 
Growth of Trees.— When timber planting is 
in order, as it most certainly will be, in a few 
years, it will be desirable to know the rate of 
growth of different trees, in order to know what 
will grow rapidly and be serviceable in a short 
time. Observation tends to show that the gro\^i:h 
for twelve years is as follows: White maple, one 
foot in diameter, thirty feet high ; ash, one foot in 
diameter, twenty feet high; white willow, one 
and a half feet diameter, fifty feet high; yellow 
willow, one and a half feet diameter, thirty-five 
feet high ; Lombardy poplar, ten inches diameter, 
forty feet high ; blue and white ash, ten inches 
diameter, twenty-five feet high; black walnut 
and butternut, ten inches diameter and twenty 
feet high. 
Diamantine.—Diamantine consists of crystal- 
lized boron, the basis of borax. The Techniker 
says that by melting one hundred parts boric 
acid and eighty parts aluminum, crystals are ob- 
tained, the so-called bort, which even attacks 
diamond. Diamantine bought in commerce is 
less hard. 
Interesting- Discovery.— Some fine carvings 
in ivory, discovered at Nineveh, showed signs of 
crumbling on arriving in England. Prof. Owen 
I concluded that the decay was caused by loss of 
albumen in the ivory, and therefore boiled the 
articles in a solution of albumen. The experi- 
ment was a success, and the ivory became as 
firm and solid as when first entombed. 
Tracing's on Glass for the Lantern.— The 
following method, by George Smith, appears to 
be satisfactory. A piece of finely ground glass is 
rubbed over with a trace of glycerine, in order to 
make it as transparent as possible. It is now 
easy to 'write or draw on the prepared surface 
with a hard and finely pointed blacklead pencil, 
and the glass is so transparent that the finest de- 
tails of any engraving over which it may be 
placed can be seen quite distinctly. The draw- 
ing having been finished, the plate is washed 
with water, in order to remove the glycerine, and 
dried. A thin coat of Canada balsam or of nega- 
tive varnish now serves to render the slide per- 
manently transparent and ready for the lantern. 
Preservation of India-rubber Tubing" 
Under Water.— Mr. Mareck relates his experi- 
ence of having met with serious annual losses', 
in consequence of certain kinds of India-rubber 
tubing soon becoming brittle on exposure. After 
many experiments, he has adopted the plan of 
preserving them under water, which he renews 
from time to time, He found that even the thick- 
est kind of tubing will thus remain soft and plia- 
ble without losing elasticity ; nor has he found 
any other drawback by adopting this plan, except 
this, that they undergo a change in appearance. 
Red or brown tubing gradually fades, and bo 
comes brownish or grayish-yellow; gray tubmg 
becomes darker and browner externally. A sec- 
tion of tubing reveals the fact that about one-half 
of the thickness of the rubber, from the outside 
towards the middle, appears bleached and fatty; 
but the change is one which is rather of benefit 
for their practical use. The author adds that 
very thin rubber bands, with which other goods 
were tied, became so soft that they could be 
rubbed to small crumbs with the fingers.— Drng^- 
Zer's Pohjt. Journ. 
