38 
THE YOUNG SCIENTIST. 
sen burner alone will suffice if the gas pressure 
is good. A good blowpipe tor heating glass 
tubes may be made out of some pieces of glass 
tubing, having a bore of about one-quarter of 
an inch in diameter. A description of such a 
blowpipe, which we have found to succeed per- 
fectly in our own practice may not be amiss 
here. In Fig. 1, a is the top of a small stand, 
in fact, an old washstand, bought at auction, 
through which are bored four holep, h, h, h, h, 
somewhat larger than the glass tubes to be 
c c 
Fig. 1. 
used. We select four pieces of tubing, two of 
them 6 inches long, and the two others about 
11 inches. Join now a short one to the side of 
a long one, about 21 inches from the end of the 
latter, so that the two will form a right angle; 
then bend the long tube down, and draw the 
short end off to a point to form the jet as seen 
at c. Do the same with the other tubes, and 
the two jets are made. They must be placed 
in the table, as shown in Fig. 1, by means of 
corks, which fit the holes in the table, the 
tubes being fitted into holes in the corks. 
Connect now the two inner tubes with the gas, 
and the two outer ones with the bellows, and 
the blowpipe is complete. There should be a 
stopcock between the bellows and each of the 
air tubes, to regulate the pressure. It is best 
to purchase a bellows, which can be had at 
moderate cost, 
If the operator is not familiar with the 
method of joining a tube at right angles to 
another, he will perhaps find some difficulty in 
doing it, and will very likely prefer to simply 
hend a single tube at a right angle, and draw 
out a jet on one end. This will be his blow- 
pipe, and the flame may be a common kero- 
sene hand lamp, with a wick about half an inch 
wide or more, or what is still better a gas 
burner made with a flat top, perforated with 
numerous small holes, across which the jet is 
directed in the line of its greatest diameter. 
This top is well made oval, and about three- 
fourths of an inch long by half an inch wide. 
In manipulating glass it is a great advantage 
to have two flames from opposite directions, 
which meet at an intermediate point, as much 
greater heat is at command, and the tube is 
heated much more evenly. 
A few general directions for manipulating 
glass tubes are all that is necessary. To bend a 
tube, the best plan is to use a common fish-tail 
gas burner as the source of heat. The deposit 
of soot is an advantage in preventing too rapid 
cooling, and can be wiped off with a bit of 
paper or cloth. Let the tube be constantly 
revolving in the fingers while heating, and 
never attempt to bend a tube or alter its form in 
any way while in the flame. When well softened, 
remove from the flame, and bend slowly and 
steadily with the fingers at a moderate distance 
from the heated portion, so as to secure an 
even curve. 
To make a good jet, or to contract the bore 
at any point, use the Bunsen burner, or, better, 
the blowpipe flame. Revolve the tube in the 
flame, and as it softens press gently together, 
so as to thicken the tube at the point heated. 
By a little practice a tube of one-quarter inch 
bore can be contracted to an almost capillary 
tube at any point, while the external diameter 
remains the same. To make a jet heat near 
the end and thicken in the same way, remove 
from the flame, and draw out slowly until the 
proper size is obtained. When the glass is 
thick enough we need simply heat and draw 
out, but usually the jet so obtained will have 
very thin walls, and hence be too fragile for 
service. 
To blow a bulb is no easy matter at first. It 
is best to use a small tube with thick walls, 
draw it off abruptly at one end, and fuse it 
together. Then hold it in the blowpipe flame, 
and soften thoroughly, keeping the cool end 
down, so that some thickening shall take 
place. When properly heated withdraw from 
flame and blow quickly in the open end until 
the bulb is large enough. Never cease revolv- 
ing in the fingers, or the bulb will be one sided. 
It will be one-sided any way until you know 
how to do it. To blow a bulb in any other 
part of a tube, follow the same general plan, 
and seal up one end or put a cork in it. 
To make a " funnel tube," like Fig. 2, blow a 
bulb on the end of a tube, then revolve the 
tube in the flame, so as to heat the top of the 
bulb, down to the dotted line, a h. This 
