94 
THE YOUNG SCIENTIST. 
be uniform tlirougiiout. The charcoal 
should previously be passed through a 
line sieve. The doughy mass is cut into 
suitable pieces, which are rolled between 
two boards dusted over with coal-dust, 
until cylindrical strips about 1 centimetre 
in thickness are formed, which are al- 
lowed to dry slowly between blotting- 
paper. When using them, one end is 
pointed like a lead pencil, and, after hav- 
ing previously made a scratch in the glass 
with a file or diamond, the heated and 
glowing end of the pencil is carried along 
the line in which the glass is intended to 
be fractured, 
•2. Dissolve 8 to 10 parts of tragacanth 
in about 100 parts of hot water, add to the 
mixture, under stirring, 30 parts of acetate 
of lead and 60 parts of tinely-sifted beach- 
wood charcoal, and proceed as in the pre- 
vious formula. 
3. Sticks of soft wood (willow or poplar), 
of about the thickness of a linger, which 
must be thoroughly dry, are immersed for 
about one week in a concentrated solu- 
tion of acetate of lead, after which they 
are again dried. When ignited these 
sticks burn like glazier's charcoal. 
The first formula is that of Berzelius, 
and yields the best product, as it burns 
much slower than the others. These 
pastils maintain a more uniform heat 
than a hot iron, which is constantly get- 
ting cold. 
Hand-Turning. 
{Continued from page go.) 
OITR remarks so far refer to such turn- 
ing as may be accomplished between 
the centres of the lathe cylinders. We 
will now proceed to the turning of such 
articles as require to be turned out after 
the fashion of a bowl. The work must be 
chucked in a different form altogether; 
in some cases on a worm chuck, in others 
a cup-chuck may be more convenient. 
Now, to turn the face of a large diameter 
is quite a different thing from turning a 
cylinder ; but having practiced the latter, 
the hand will have become used to the 
holding of the gouge, and the difference 
in position and angle of the tool necessary 
will, to a certain extent, suggest itself. 
The T-rest will be now more convenient, 
if lowered, to allow of the cutting edge of 
the tool being brought nearly to the 
centre ; the same motion as derived by the 
left hand being on the top of the tool and 
the right holding the handle, as in turn- 
ing between centres, will now be obtained, 
only it will be applied to the surface. In 
turning out a bowl, for instance, the gouge 
must be turned on to its side until the left 
side becomes the upper part, and, accord- 
ing to the curve and depth of bowl re- 
quired, the right hand must be moved to 
form the desired sweeep, and at the same 
time the gouge allowed to slide gradually 
through the left hand, which hand, al- 
though released to allow of this move- 
ment, must still retain sufficient hold, and 
not allow the tool to go where it is not 
wanted, I dare say, however, that it will 
insist upon taking a different course to 
that actually desired in the first few trials. 
I think we may turn our attention to the 
production of something useful in the 
shape of a box for some actual purpose, 
viz., for holding string. I start with this 
because it will give opportunity for further 
advance, as it will require several chuck- 
ings. Before beginning this, I think a 
few hours at screw-cutting will be of great 
service. Soft wood screws are generally 
made with what are termed screw boxes, 
which are to be had at all the tool shops, 
and are made from a very small size to 
the size of bench screws, about 25 or 3 in. 
diameter. These, however, will not serve 
the purpose now requisite; therefore, a 
little practice and patience must be used, 
and I think it will be overcome. To begin 
with, when about to make anything that 
will require a screw, a w^ood of closer 
grain will be better, and I should choose 
a piece of good, sound, well-seasoned box- 
wood. In what we call striking a screw, 
the front edge of the wood should be 
rounded off, the screw tool held in right 
hand, with the thumb of left hand on the 
top over the T-rest, the hand itself passed 
round the body of the rest, and held 
firmly. A circular motion must be given 
with the right hand, and the centre part 
of the chaser will be that which first 
comes in contact with the work. It will 
only be after several trials that anything 
