path: root/73841-0.txt

*** START OF THE PROJECT GUTENBERG EBOOK 73841 ***





                       Experimental Glass Blowing
                                FOR BOYS


                                   BY
                       CARLETON J. LYNDE, PH. D.
                          Professor of Physics
               MacDonald College, Quebec Province, Canada


                    Prepared under the direction of
                           ALFRED C. GILBERT
                         YALE UNIVERSITY, 1909




                       EXPERIMENTAL GLASS BLOWING


Boys, glass tubes are made in the sizes shown in Fig. 2, and in larger
sizes. You will use sizes 2, 4, and 6 in the following =experiments=.


Experiment 1. Fun bending glass.

[Illustration:

  FIG. 2

  SIZES OF GLASS TUBING
]

Hold a piece of No. 2, with both hands, in the flame of the alcohol
lamp, and turn it constantly (Fig. 3). Do you find that when the glass
becomes nearly red hot, it becomes soft and bends easily?

[Illustration:

  FIG. 3

  HEATING GLASS TO SOFTEN IT
]

Take the tube out of the flame, bend it into any shape you wish (Fig.
4), and allow it to cool. Do you find that the glass hardens when it
cools and retains the bent shape?

Heat the tube near the first bend, turn it constantly, take it out of
the flame, and make another bend.

Repeat this and make all kinds of fantastic shapes.

Place all hot glass on the cooling blocks, not on the table.

Glass is used in many, many ways by the human race; for example, to make
bottles, tumblers, window glass, and so on, and all of these uses depend
upon the facts which you have just illustrated, namely, that glass
becomes soft when heated and hard when cooled again.

[Illustration:

  FIG. 4

  BENDING GLASS
]


                                THE LAMP

The wick should be cut straight across and should project above the wick
holder about ⅛ inch (Fig. 5), or a little more if you require more heat.
Burn wood alcohol or grain alcohol, because they give flames without
soot or smoke. Fill the lamp to within a ½ inch of the top only; it will
burn one hour. The hottest part of the flame is not down close to the
wick, as most beginners suppose, but up just beneath the tip.

[Illustration:

  FIG. 5

  THE LAMP
]

Buy your alcohol at a drug store in quantities of one pint or more. When
you are through experimenting for the day pour the alcohol from the lamp
back into the pint bottle and cork the bottle tightly. Alcohol left in
the lamp gradually evaporates and is lost.

Do not let the lamp stand with alcohol in it for any considerable
time—overnight for example—because fuel alcohol contains water and when
it evaporates from the wick, the alcohol evaporates first and leaves the
water in the wick. Then when you try to light the wick again, you will
find that you cannot do so, because, of course, water does not burn. If
this happens to you, take the wick out, dry it, and start the lamp
again.

[Illustration:

  FIG. 6

  MAKING A SCRATCH
]

It is perfectly safe to use kerosene in the lamp, but it gives a very
smoky flame which deposits soot on the glass and fills the air with soot
particles. Your mother will object very strenuously to this because the
soot particles settle and blacken everything. Burn alcohol only, at
least in the house.


Experiment 2. To cut glass tubing.

[Illustration:

  FIG. 7

  BREAKING THE TUBE
]

Cut off a six-inch length of No. 2 as follows: Lay the tube flat on the
table, mark the six-inch length and draw the file across the tube at
this point, pressing hard enough to make a good scratch (Fig. 6). Grasp
the tube with both hands near the scratch, as in Fig. 7, pull apart and
bend slightly. Do you find that the tube breaks across easily?

Repeat this with No. 4 and No. 6 tubes.


Experiment 3. To make the edges smooth.

[Illustration:

  FIG. 8

  MAKING THE EDGES SMOOTH
]

Hold one end of the six-inch piece of No. 2 in the tip of the flame
(Fig. 8), and turn constantly until it is just red hot. Take it out and
let it cool on the blocks. Do you find that the edges are smooth?

Repeat with the other end.

Repeat with both ends of the six-inch piece of No. 4.

If thick glass is heated quickly it may crack, because the hot exterior
expands more quickly than the cooler interior and produces internal
strains.

[Illustration:

  FIG. 9

  THE BLOWPIPE FLAME
]

The No. 6 tube is comparatively thick and should be heated =gradually=
as follows: Hold the end in the flame for about 1 second, then withdraw
it for about 1 second; hold it in the flame again for 1 second, and
withdraw it for 1 second. Repeat this eight or ten times, then hold and
turn it in the flame until red hot.

Smooth both ends of the No. 6 piece in this way.


Experiment 4. Practice with the blowpipe.

Hold the small end of the blowpipe just inside the flame at one edge,
about ⅛ inch above the wick (Fig. 9), and blow air through the flame
parallel to the top of the wick.

Keep your mouth closed on the blowpipe, =breathe through your nose=, and
=practice keeping a steady stream of air going for a long time=. You
will be able to do this with a little practice.

Do you observe that the blowpipe flame is pointed, also that it is made
up of a pointed cone inside and a lighter-colored cone outside? The
hottest part of the flame is inside the outer cone just beyond the point
of the inner cone.

[Illustration:

  FIG. 10

  CLOSING ONE END OF A TUBE
]

The blowpipe flame is hotter than the lamp flame because the heat of the
burning alcohol is concentrated at one point by means of the air blast,
and because the alcohol is more completely burned by the extra air.


Experiment 5. To close the end of a small tube.

Hold one end of a piece of No. 2 tube in the blowpipe flame (Fig. 10),
turn it slowly, and heat until the end closes. Does it close nicely?

Close one end of a piece of No. 4 in the same way.

You can close No. 6 tubing in this way, but it leaves a large lump of
glass which may crack on cooling or on reheating. You will practice
closing No. 6 tubing later.


                            The “why” of it

The glass becomes soft when heated because it becomes almost a liquid,
and if it is heated sufficiently it becomes entirely a liquid. In this
respect it acts very much as pitch, rosin, and wax act when heated by
the sun or by a fire.

[Illustration:

  FIG. 11

  MAKING A GLASS BUBBLE
]

The end of a glass tube becomes smooth, or closes entirely, when heated,
for the following reason: The surface of any liquid tries to take the
smallest possible area (this is explained in detail under “Surface
Tension” in the Gilbert book on “Experimental Mechanics”), for example,
a small particle of water takes the shape of a drop, a sphere, and the
surface of a sphere has the least area for a given amount of water. Now
when the end of the glass tube is heated it becomes a liquid, and the
surface of this liquid contracts the glass into a smooth rounded surface
of least area. If the tube is heated still more, the surface contracts
still more and closes the end.


Experiment 6. Fun blowing glass bubbles.

Smooth one end of a piece of No. 2 tube and allow it to cool. Close the
other end in the blowpipe flame, turn it slowly, and heat until it is
very hot. Take the tube out of the flame, put the smooth end into your
mouth quickly, and blow as hard as you can (Fig. 11). Do you get a fine
big glass bubble which bursts with a pop?

If you get only a small bulb at the first trial, heat the end, and try
again. Do you find that the bulb shrinks when heated but blows out again
readily?

[Illustration:

  FIG. 12

  BLOWING A BULB
]

When you get a big bubble, place the bubble end of the tube on a cooling
block and break all the thin glass away from the tube by striking it
with the file or blowpipe. Then close the end and blow another bubble.

Repeat until you can blow bubbles easily.

Repeat with a piece of No. 4 tube.


                             BUBBLE COLORS

[Illustration:

  FIG. 13

  A WATER BALLOON
]

Do you find that the thin glass of the bubbles shows colors, especially
in sunlight, just as soap bubbles do? You boys who have had the Gilbert
set on “Light Experiments” will know that these colors are due to
“interference.” The colors produced by a thin film of oil on water are
also produced by “interference.”


Experiment 7. To make water balloons.

Close one end of the No. 2 tube in the blowpipe flame again and while it
is still hot blow carefully into the open end until you have a bulb
about ½ inch in diameter (Fig. 12). Now let it cool. Make a scratch with
the file about ¼ inch from the bulb, break the tube at this point (Fig.
13), and smooth the rough edge.

[Illustration:

  FIG. 14

  THE BALLOON SINKS AND RISES
]

Put the bulb in a tumbler of water. Does it float? If not, make another
balloon with a larger bulb.


Experiment 8. Magic.

Find a large bottle made of clear glass, the neck of which will fit your
solid rubber stopper.

Fill the bottle with water =to overflowing=, insert the balloon, and
then the stopper.

Now press down hard on the stopper. Does the balloon sink in a most
magical manner (Fig. 14)?

Release the stopper. Does the balloon rise in an equally magical manner?

[Illustration:

  FIG. 15

  A BALLOON RACE
]


Experiment 9. Balloon races.

Make another water balloon. Put the two balloons together in the bottle
filled to overflowing with water.

Insert the stopper and press down hard. Do the balloons sink (Fig. 15),
and does one sink more quickly than the other?

Release the stopper. Do the balloons rise, and does one rise more
quickly than the other?

The most buoyant balloon sinks last and rises first.


                            The “why” of it

[Illustration:

  FIG. 16

  DRAWING A THIN TUBE
]

You boys who have the Gilbert set on “Hydraulic and Pneumatic
Engineering” will know the “why” of the last three experiments. Any body
floats in water if it is lighter than an equal volume of water, and it
sinks if it is heavier than an equal volume of water. Water is
practically incompressible but air is very compressible: thus when you
press down on the stopper, you force water into the balloon and compress
the air in it; when you release the stopper, the compressed air in the
balloon expands and drives the water out. When the weight of the balloon
and the weight of the water in it are together greater than the weight
of water displaced by the balloon, the balloon sinks; when they are
less, it rises.


Experiment 10. Fun with thin tubes.

Hold a piece of No. 2 tubing in the lamp flame and turn it constantly.
When it is red hot and soft, =take it out of the flame= and pull your
hands apart until the tube is stretched ten or twelve inches (Fig. 16).
Is the tube in the shape shown in Fig. 17?

[Illustration:

  FIG. 17

  A GLASS TUBE STRETCHED
]

Allow the tube to cool, break the large ends away from the thin tube,
place one end of the thin tube in a glass of water, and blow into the
other end to make air bubbles in the water (Fig. 18). If you can do so,
it is a real tube.

[Illustration:

  FIG. 18

  AIR THROUGH TUBE
]

Does the thin tube bend easily and does it spring back when released?

Repeat the experiment with another piece of No. 2 tubing, but make the
thin tube as long as you can.

Can you blow air through the thin tube, and does it bend very easily
indeed?

Repeat with a piece of No. 4 tubing.

These thin hairlike tubes are called “capillary” tubes, from the Latin
word =capillus=, meaning a hair.


Experiment 11. Magic.

[Illustration:

  FIG. 19

  WATER RUNS UPHILL
]

You have always heard that water runs =downhill=, but you will now see
it run =uphill= and remain there in a most =magical= manner.

Cut off 5-inch lengths of No. 6, No. 4, and No. 2 tubing, stand them
side by side in a glass full of water (Fig. 19), and move them up and
down in the water to wet the inside of the tubes.

Now look at the water level in each of the tubes. Is it above the level
of the water in the glass, and is it higher the smaller the inside
diameter of the tube, that is, is it higher in the No. 2 than in No. 4,
and in No. 4 than in No. 6?

Now take the thin capillary tube which has the largest inside diameter,
place one end in the glass of water, suck it full of water and blow it
out. Now with one end in the glass of water notice quickly how the water
rises inside the tube. Does it run =uphill= in a most magical manner
(Fig. 20), and does it remain there?

[Illustration:

  FIG. 20

  WATER RUNS UP TUBE
]

Repeat this with your other capillary tubes. Does the water run uphill
in each, and does it rise higher the smaller the inside diameter of the
tube?

The “why” of this is explained in Gilbert’s “Experimental Mechanics”
under “Capillarity.”


                             WHAT IS GLASS?

Common glass is made from three substances with which you are all more
or less familiar; namely, sand, sodium carbonate (washing soda), and
lime.

If sand and soda or potash are mixed and heated to a high temperature,
they melt together and produce a glass which dissolves in water. This is
known as “water glass” and it is used in many ways: to preserve eggs, to
cement fire bricks, to make fireproof cement, and so on. If, however,
lime is added and the mixture is heated to a high temperature, a glass
is produced which is not soluble in water. This is the glass you know.

The three most common kinds of glass are: Venetian glass, made from
sand, soda, and lime; Bohemian glass, from sand, potash, and lime; and
crystal or flint glass, from sand, potash, and lead oxide.

[Illustration:

  FIG. 21

  SECOND STEP IN MAKING WINDOW PANES
]

[Illustration:

  FIG. 22

  IRONING THE CYLINDERS FLAT
]


                     HOW ARE THINGS MADE OF GLASS?

The glass mixture is heated to a high temperature in fire clay pots or
tanks in large ovens. The surface is skimmed from time to time and the
heating is continued until all air bubbles have escaped from the
mixture, usually about three days.

The glass is now quite fluid and it is allowed to cool somewhat until it
is viscous; then the objects are made by blowing, pressing, or rolling,
as described below.

The finished articles are finally “annealed,” that is, they are placed
while still hot in a second hot oven, which is then sealed and allowed
to cool slowly, for four or five days or for as many weeks, according to
the kind of glass.

If a glass object cools quickly, it cools more rapidly on the surface
than in the interior. This produces a condition of strain in the glass
and the object may drop to pieces when jarred or scratched. This
condition of strain is avoided by allowing the objects to cool very
slowly, that is, by annealing.


                              WINDOW GLASS

Window glass is blown in exactly the same way as you have blown glass
balloons; the process is illustrated in Fig. 1.

The glass mixture is heated for about three days in fire clay pots and
is allowed to cool until it is viscous. The glass blower then attaches a
lump of the viscous glass to the end of a straight iron blowpipe about
five feet long and blows a bulb. He then reheats the glass and blows a
larger pear-shaped bulb and in doing so rests the glass on a pear-shaped
mold of charred wood (see center of Fig. 1). He again reheats the glass,
holds the pear-shaped bulb over a pit, and blows a long cylinder (see
left of Fig. 1).

The ends of the cylinder are now cut off and the edges are smeared with
molten glass to prevent splitting (see right, Fig. 21). The cylinder is
next cut lengthwise with a diamond (center, Fig. 21), and is placed in a
second hot oven, where it is ironed out flat (Fig. 22).

[Illustration:

  FIG. 23

  BOTTLES BLOWN IN A MOLD
]

The flat sheets are finally annealed in a third oven for a number of
days and are then cut into panes, sorted, and packed.


                              GLASS TUBES

[Illustration:

  FIG. 24

  ROLLING PLATE GLASS
]

The glass tubes with which you do the experiments in this book are made
in the same way as window glass up to the stage of blowing the cylinder;
then the blower’s helper attaches an iron rod to the opposite end of the
cylinder (see right of Fig. 1), and the blower and helper walk backward
away from each other to pull the cylinder into a tube. Of course, they
use a small amount of glass to make small tubes, and larger amounts for
large tubes.


                              MOLDED GLASS

Many articles of glass are made by blowing the glass in molds. Bottles
are made in this way (Fig. 23), and large machines are now in use which
mold many bottles at one time in this way.


                             PRESSED GLASS

Many articles are made by pressing glass into molds, that is, the molten
glass is poured into molds and is pressed against the sides of the mold
by means of a plunger. Imitation cut glass is pressed in this way.


                              PLATE GLASS

The large sheets of plate glass used in store windows are not blown, but
rolled. The molten glass is poured from the fire clay pots upon a
cast-iron table and is rolled flat by means of a large iron roller (Fig.
24). The glass is then in the shape of plate glass, but is rough on both
sides. It is annealed for a number of days and then is ground smooth on
both sides, first with coarse emery, then with finer and finer emery,
and is finally polished with rouge. The result is the beautifully
polished plate glass we see in large windows.


                             OPTICAL GLASS

The United States and Great Britain made great strides in the
manufacture of optical glass during the war and there are now many kinds
on the market. They are used in making the lenses, prisms, and mirrors
for optical instruments.

Optical glass is made in much the same way as ordinary glass, but great
care is taken: first, to see that the materials are pure; second, to
stir the glass constantly, as it cools from the molten to the viscous
state, to make it as uniform as possible; and third, to cool it very
slowly in the annealing process, to avoid strains.


                              QUARTZ GLASS

[Illustration:

  FIG. 25

  A POLLYWOG
]

An entirely new glass has been placed on the market in quantity in
recent years. It is made by melting very pure quartz sand at a
temperature of 3000° F. and cooling it fairly rapidly. It has the very
valuable property of expanding and contracting very, very slightly when
heated and cooled. Thus there is practically no internal strain set up
when it is heated or cooled quickly and it does not break. It can be
heated red hot, for example, and then plunged into cold water without
breaking. It is probable that this glass will be in universal use in a
very few years.


Experiment 12. To make an acrobatic pollywog.

Smooth one end of a piece of No. 2 tube to put in your mouth, close the
other end in the blowpipe flame, take it out and blow a bulb about ½
inch in diameter.

Allow the bulb to cool, then heat the tube about ¼ inch from the bulb
and draw it out into a thin tube. Now bend the thin tube at right angles
near the bulb and break it off (Fig. 25).

Place the bulb in water. Does it float? If not, blow another with a
larger bulb.


Experiment 13. Magic.

[Illustration:

  FIG. 26

  ACROBATS
]

Place the pollywog in a bottle filled to overflowing with water, insert
the solid rubber stopper, and press it down hard. Does the pollywog
sink?

Now release the stopper quickly. Does the pollywog turn somersaults in a
most magical manner (1, Fig. 26), and also rise?

Make one or two more pollywogs, place them all in the bottle together
(2, Fig. 26), and entertain your friends with a pollywog circus.

The pollywog sinks when you press down on the stopper because you
compress the air in it and force water in until it weighs more than the
water it displaces.

[Illustration:

  FIG. 27

  DANCING POLLYWOGS
]

The pollywog rises when you release the stopper because the compressed
air drives the water out until the pollywog weighs less than the water
it displaces.

The pollywog turns a somersault because the water rushes out sidewise in
one direction and forces the nozzle in the other direction.

Air may escape from the pollywog when it is turning a somersault; if so,
water will take its place, and may make the pollywog too heavy to float.
You can restore its buoyancy by sucking out the water.


Experiment 14. A dancing pollywog.

[Illustration:

  FIG. 28

  DRAWING GLASS SPIDER-WEBS
]

Make a pollywog as in Experiment 12, but bend its tail twice as shown in
1, Fig. 27; the nozzle is at one side and points sidewise.

[Illustration:

  FIG. 29

  THE SPIDER TRICK
]

Put it in the bottle full of water, then press down and release the
stopper. Does it sink and rise, and does it also whirl around most
beautifully as it rises?

Make another pollywog (2, Fig. 27), but bend its nozzle in the opposite
direction. Does it whirl in a direction opposite to that of the first
pollywog?

Put them in the bottle together and treat your friends to a pollywog
dance.

The pollywog whirls because the water rushes out of the nozzle in one
direction and forces the nozzle in the opposite direction.


Experiment 15. To make glass spider-web.

Heat the end of a piece of No. 2 tube in the blowpipe flame until it is
melted and very hot. Now touch the end of another piece of glass to the
melted glass, remove from the flame, and quickly pull the two pieces
apart as far as you can (Fig. 28). Do you find that you have pulled part
of the melted glass out into a very fine glass spider-web?

Repeat, but ask a friend to touch the second piece of glass to the first
and run away as fast as he can.

Do you get a much finer spider-web?

Is the glass spider-web fairly strong and very flexible?


Experiment 16. The ancient spider trick.

[Illustration:

  FIG. 30

  ATTACHING A HANDLE
]

Attach an imitation spider—or the dead body of a real spider—to the end
of the glass spider-web and surprise your friends, as shown in Fig. 29.
The glass spider-web is much less visible than a thread for this
purpose.


Experiment 17. To make working handles.

You can save glass in many cases by attaching a short piece of glass to
the piece you intend to work with, as follows: Heat an end of each piece
in the lamp flame until red hot, press them together, remove from the
flame, and hold until solid. The short piece then serves as a working
handle (Fig. 30) for the large piece.


Experiment 18. To close a large tube.

You closed small tubes in Experiment 5 by simply heating the end in the
blowpipe flame. This method does not serve for large tubes, however,
because it leaves a very large lump of glass which may crack on cooling
or reheating.

[Illustration:

  FIG. 31

  CLOSING A LARGE TUBE
]

[Illustration:

  FIG. 32

  MAKING A SUBMARINE
]

Practice the following method of closing a large tube; first with a
piece of No. 4 tube, and then with a piece of No. 6: Attach a working
handle to the end to be closed, heat the tube ½ inch from the end in the
blowpipe flame, turn constantly, and when soft pull apart until the tube
has the shape 1, Fig. 31. Heat, turn, and pull the end away to leave the
tube as in 2. Heat the end and blow out until it has the shape 3. The
end is now closed and the glass has about the same thickness as the
remainder of the tube.


Experiment 19. To make a submarine.

Close one end of a piece of No. 2 tubing as described above, but leave
the end somewhat pointed (1, Fig. 32). Heat the tube on one side at a
distance ½ inch from the end and blow a bulb about ½ inch in diameter
(2). Heat the tube ¼ inch from the bulb, draw it down into a fine tube,
and break off the tube, leaving a small hole in the end (3). Place the
submarine in a glass of water, and if it floats it is complete.


Experiment 20. Magic.

[Illustration:

  FIG. 33

  THE SUBMARINE SUBMERGES
]

Fill a bottle to overflowing with water, insert the submarine open end
down, insert the solid rubber stopper and press down hard (Fig. 33).
Does the submarine submerge?

Release the stopper. Does the submarine rise and does it also move
forward?

Turn the bottle on its side and release the stopper quickly. Does the
submarine shoot forward at a great rate (Fig. 34)?

The submarine acts in this magical manner for the reasons given in
Experiment 9. When you press the stopper in, you compress the air in the
submarine and force water in until the submarine weighs more than an
equal volume of water and it sinks. When you release the pressure on the
stopper, the compressed air forces the water out until the submarine
becomes lighter than an equal volume of water and it rises. The water
rushing out through the opening exerts pressure backward on the water in
the bottle and the reaction drives the submarine forward.


Experiment 21. Fun with the submarine.

If your friends do not know about the little submarine, you can mystify
them as follows: Tell them that submarines are just like other fish;
namely, they lay eggs, and the little eggs hatch out after a certain
number of days (of course, your friends will know that you are only
joking). Pretend that you found one of these submarine eggs, hatched it
out in lukewarm water, and that you have trained the baby submarine to
do some simple tricks. For example, that you have trained it to
submerge, rise, and attack, when you issue the commands “submerge,”
“rise,” and “attack.”

[Illustration:

  FIG. 34

  THE SUBMARINE SHOOTS FORWARD
]

Tell them to watch the submarine carefully and to notice that it takes
in water and submerges when you issue the command “submerge.” Stand the
bottle on the table, issue the command “submerge” and, while your
friends are watching the submarine, press down on the stopper unknown to
them.

[Illustration:

  FIG. 35

  A SUBMARINE BATTLE
]

Tell them to watch the submarine carefully again and to notice that it
expels water and rises when you issue the command “rise.” Issue the
command and unknown to them release the pressure on the stopper slowly.

Repeat with the command “attack” and release the pressure quickly.


Experiment 22. A submarine battle.

Make a second submarine, place it in a large bottle with the first
submarine, turn the bottle on its side, and make the submarines manœuver
by moving the stopper in and out.

[Illustration:

  FIG. 36

  FLARING A TUBE
]

Finally arrange them so that they are on the bottom, facing each other
bow to bow, two or three inches apart (1, Fig. 35), and release the
stopper quickly. Do the submarines try to ram each other (2, Fig. 35) in
a most realistic manner?

[Illustration:

  FIG. 37

  AN AIR GUN
]


Experiment 23. To flare the end of a tube.

Heat the end of a piece of No. 2 tube until it is red hot, take it out
of the flame, hold the flaring wire inside the end, and press outward
gently while you revolve the tube (1, Fig. 36). Do you find that the end
is flared out (2, Fig. 36)?


Experiment 24. To make an air gun.

Take a full length piece of No. 4 tube and flare both ends slightly.
This is the air gun (Fig. 37).

Now to make an arrow, cut off the lighting end of a match and insert a
pin in the other end (Fig. 38).

[Illustration:

  FIG. 38

  THE ARROW IS SHOT PIN-END FIRST
]

Insert this arrow in the air gun and blow it out. Does it come out with
considerable speed?


Experiment 25. A shooting match.

[Illustration:

  FIG. 39

  A SHOOTING MATCH
]

Draw a target on a piece of paper and hang it up, away from the wall or
at the edge of the table, where there will be space behind for the
arrows to pass through. Now shoot at the target with your air gun (Fig.
39). Do you find that the arrow makes holes in the target and sometimes
goes right through?

The bull’s-eye of a target is usually 1 inch in diameter, the next
circle outside is 2 inches in diameter, the next 4 inches, and the outer
circle 5 inches.

Get up a shooting match and keep track of the score made by each.

If the bull’s-eye is cut anywhere by the arrow, the count is 5 points; a
cut anywhere inside or touching the 2-inch circle counts 4 points;
anywhere inside or touching the next two circles counts 3 and 2 points
respectively.

The one who makes the highest score in five shots is the winner.

It is more sanitary if each shooter has his own air gun and arrows.


Experiment 26. Height and distance contest.

Go outside and see which of you can shoot his arrow to the greatest
height and to the greatest distance.

Give each contestant five shots.

[Illustration:

  FIG. 40

  THE PEA SHOOTER IN ACTION
]

You can make fair estimates of the heights if you shoot up beside a
building or tall tree.


Experiment 27. To make a pea shooter.

[Illustration:

  FIG. 41

  BENDS
]

Take a full length piece of No. 6 tubing, smooth both ends and flare
them out slightly. This makes an excellent pea shooter. Try it with
peas. Do you find that they come out with great speed?


Experiment 28. A pea-shooting match.

Make a target on a piece of paper, hang it up away from the wall or at
the edge of the table, and shoot at it (Fig. 40). Do you find that the
peas go right through the paper?

Arrange a match with your friends and keep track of the score as in
Experiment 25.


Experiment 29. To make a good bend.

A good bend has the same diameter in the bend as in the remainder of the
tube (1, Fig. 41). It is rather difficult to make because the tube tends
to cave in on the inside of the bend (2) or flatten on the outside (3),
or both.

[Illustration:

  FIG. 42

  A DRINKING TUBE
]

Make the bend as follows: Heat a piece of No. 2 tube about 2 inches from
one end in the lamp flame, turn it constantly and move it back and forth
endwise to heat a length of about 2½ inches. When soft, take the tube
out of the flame, and bend the ends =upward= until the angle is 90°.

If the bend is flat on the inside or outside, close one end of the tube
in the blowpipe flame, smooth the other end and allow them to cool, then
heat the flat side of the bend in the blowpipe flame and blow it out
slightly. This makes the diameter of the tube at the bend equal to that
of the remainder of the tube. Cut off the closed end, smooth the edge,
and your bend is complete.

Make bends with No. 4 tube.

[Illustration:

  FIG. 43

  A SIPHON
]


Experiment 30. To make a drinking tube.

Many times when there is sickness in the house, it is convenient to have
a glass drinking tube (Fig. 42), through which the patient can drink
without raising his head.

Make such a tube from a piece of No. 4 tubing. The short arm is equal in
length to the depth of the tumbler; the long arm, or mouthpiece, is
about 1 inch longer than this.


Experiment 31. To make a siphon.

Cut off a piece of No 4 tubing 8 inches long, make two right-angled
bends about 1 inch apart at the center, smooth both ends, and your
siphon is complete (Fig. 43).

[Illustration:

  FIG. 44

  A SIPHON
]


Experiment 32. Magic.

Put one arm of the siphon in a tumbler of water and suck air out of the
other end. Does the water start running and does it continue to run in a
most magical way (Fig. 44) until the water is below the end of the
siphon in the tumbler?

[Illustration:

  FIG. 45

  FROM THE HIGH LEVEL TO THE LOW
]

Fill the tumbler with water again, start the water running, put the
outer arm of the siphon in an empty tumbler, and stand both tumblers on
the table (Fig. 45). Does the water run up one arm of the siphon and
down the other into the empty tumbler? Does it stop running when the
levels are the same?

Stand the first tumbler on a book. Does the water run again and stop
when the levels are again the same (Fig. 46)?

Place the lower tumbler on the book and the upper tumbler on the table.
Does the water now run in the opposite direction until the levels are
again the same?

Raise one tumbler a foot or so above the table. Does the water run up
over the edge and drop into the second? Now before the upper tumbler is
empty, lower it in such a way that an arm of the siphon is in each
tumbler, and raise the second tumbler. Does the water now run in the
opposite direction?

[Illustration:

  FIG. 46

  THE WATER STOPS WHEN LEVELS ARE THE SAME
]

You boys who have the Gilbert set on “Hydraulic and Pneumatic
Engineering” will know that it is the pressure of the atmosphere which
causes the water to run up over the edge of the tumbler in this magical
way.


Experiment 33. A long-armed siphon.

[Illustration:

  FIG. 47

  SIPHONING WITH LONG TUBES
]

Attach a full length of No. 4 tube to each arm of the siphon, as in Fig.
47, and repeat the experiments described above.

=Note=: When you insert a glass tube into a rubber coupling or rubber
stopper, wet the end of the glass tube and the inside of the coupling or
stopper, grasp the tube near the end to be inserted, and insert with a
twisting motion.


Experiment 34. To make a nozzle.

Attach a working handle to one end of a piece of No. 2 tube, heat the
tube about one inch from the end in the lamp flame, turn constantly
until soft, then remove from the flame, and draw it out about 3 inches.
When cool, break off the thin tube, cut off the nozzle to a length of
about 2½ inches, smooth the large end, and your nozzle (Fig. 48) is
complete.


Experiment 35. To make a fountain.

Arrange the apparatus as in Fig. 49, and suck air out of the nozzle.
Have you made a beautiful fountain?

[Illustration:

  FIG. 48

  A NOZZLE
]

[Illustration:

  FIG. 49 FIG. 50 FIG. 51 FIG. 52

  YOU MAKE A NUMBER OF MAGIC FOUNTAINS
]


Experiment 36. Magic.

Make a nozzle 6 inches long out of No. 2 tube. Smooth the ends of the
nozzle, and long tubes. Arrange the apparatus as in Fig. 50 and suck air
out of the nozzle until the water runs in the siphon. Does the water
squirt out of the nozzle in a magical manner?


Experiment 37. More magic.

Arrange the No. 2 apparatus as in Fig. 51, with the nozzle inside the
bottle. Now to start the apparatus: Fill the bottle about quarter full
of water, insert the tubes in the stopper as shown; insert the stopper
into the mouth of the bottle; invert the bottle; then put the short tube
in a tumbler full of water and the long tube in an empty pail or basin.
Is there a magical fountain inside the bottle?

Repeat this with a taller bottle, if you can find one to fit your
two-hole stopper. Do you get a higher fountain?


Experiment 38. Still more magic.

[Illustration:

  FIG. 53

  STARTING A SIPHON
]

Make another nozzle and attach it to the apparatus used in the last
experiment by means of the inverted siphon (Fig. 52). Start the
experiment as described above. Do you get two fountains?


Experiment 39. To start a siphon.

[Illustration:

  FIG. 54

  SIPHONING SAND
]

You can start a siphon without sucking the air out of it as follows:
Fill the siphon with water, put a finger over each end (1, Fig. 53),
place one end in a tumbler full of water and remove the finger under
water (2, Fig. 53), then remove the other finger. Does the siphon start?

In this case the water you pour into the siphon drives the air out, and
this is the reason you do not need to suck the air out.


Experiment 40. To siphon sand or mud.

Arrange a siphon (Fig. 54), start the water flowing, and then pour sand
or mud into the upper tumbler. Is the sand of mud siphoned over into the
lower tumbler?

[Illustration:

  FIG. 55

  A SQUIRT BOTTLE
]

Attach a long tube to the outer arm of the siphon and repeat the
experiment. Is the sand or mud siphoned more rapidly and more
thoroughly?


Experiment 41. To make a squirt bottle.

[Illustration:

  FIG. 56

  SQUIRT BOTTLE IN ACTION
]

Make a nozzle at one end of a piece of No. 2 tubing, make a bend near
the nozzle, cut off the other end at such a length that it will reach to
within ¼ inch of the bottom of the bottle, smooth this end, allow it to
cool, wet the tube and the two-hole stopper, shove it through one hole
of the stopper, insert an elbow in the other hole, and your squirt
bottle is complete (Fig. 55).

Fill the bottle with water, and blow through the elbow. Do you get a
fine long stream from the nozzle (Fig. 56)?

[Illustration:

  FIG. 57

  TUBE FOR TRICK SQUIRT BOTTLE
]


Experiment 42. To make a trick squirt bottle.

You can have any amount of fun with a trick squirt bottle. It is exactly
the same as the squirt bottle described in Experiment 41 except that it
has a hole just below the bend (Fig. 57).

[Illustration:

  FIG. 58

  MAKING A SMALL HOLE
]

To make the hole, make the long bent nozzle as in the last experiment,
then heat the tube just below the bend in the blowpipe flame, touch a
piece of glass tube to the red-hot glass (1, Fig. 58), and pull it away
(2, Fig. 58). Do you find that the hot glass is pulled out into a thin
pointed tube? Break off the thin tube close to the large tube, heat in
the blowpipe flame until the edges are smooth and at the same level as
the sides of the large tube. Flare the edges of the hole, if necessary;
it should be about ⅛ inch in diameter.

[Illustration:

  FIG. 59

  TRICK SQUIRT BOTTLE
]

Now fill the bottle with water, and blow hard (Fig. 59). Do you find
that one stream of water is driven into your face and another out of the
nozzle?


Experiment 43. Fun with a trick squirt bottle.

[Illustration:

  FIG. 60

  TRICK BOTTLE IN ACTION
]

Now to have fun with your trick bottle, show it to one friend at a time.
Do not ask him to try the bottle, just go where he can see you and
squirt a long stream, but unknown to him have your finger over the hole
below the bend.

[Illustration:

  FIG. 61

  A SIMPLE ENGINEER’S LEVEL
  (_From Aldous’ Physics. Courtesy of The Macmillan Company_)
]

Your friend will just naturally want to have a try at it. So you say
“All right, let’s see who can squirt the longest stream.” Tell him that
all he has to do is to take a deep breath and blow as hard as he can. He
will do so, with laughable results (Fig. 60).

Now together find another friend. Do not ask him to blow, but each of
you blow as long a stream as you can, where he can see you. He will beg
to be allowed to try, and finally you let him, with the same laughable
results.

[Illustration:

  FIG. 62

  ONE-LEGGED TABLE AND LEVEL
]

Repeat with other friends.


Experiment 44. To make an engineer’s level.

You can make one form of engineer’s level (Fig. 61) as follows: Take a
full length of No. 6 tubing, bend it up 4 inches at each end, smooth the
ends, attach it to a small board, rest the board on a one-legged table,
and you have a serviceable level (Fig. 62).

Fill the tube with water, shove the pointed end of the leg into the
ground and sight along the outside of the upright tubes at the level of
the water surfaces. The line along which you sight is exactly
horizontal, because the water surfaces are at exactly the same level.


Experiment 45. To use the engineer’s level.

[Illustration:

  FIG. 63

  HOMEMADE LEVEL IN USE
]

An engineer’s level is used to find the difference in level of two or
more points (Fig. 63).

To practice using your level, find the difference in level of two points
100 feet apart on a road, sidewalk, or railroad.

To do this, you must first make what is called a leveling rod. Find a
piece of wood about one or two inches square and six or more feet long,
mark on it feet and inches, beginning at the bottom end, and your
leveling rod is complete.

Now to find the difference in level of two points 100 feet apart,
scratch a line or insert a small stake at one point, then pace off 100
feet and mark the second point. Now set up your level between the two
points, ask a friend to hold the rod on the ground and upright, at the
first point, sight along the water levels at the rod, and ask your
friend to move his finger, or a white card, up and down until it is
exactly in your line of sight. Now ask your friend to tell you exactly
where his finger or card is and record this height. Let us suppose that
it is 4 feet 6 inches above the ground. Now leave the level exactly
where it is, ask your friend to hold the rod upright at the second
point, and again sight along the water levels at the rod. Let us suppose
that his finger or card is now exactly 3 feet above the ground.

The difference in level at the two points is 4 feet 6 inches minus 3
feet or 1 foot 6 inches. That is, the second point is 1½ feet above the
first point or the grade is 1.5 feet in 100, or 1.5 per cent.

You can now mark a third point 100 feet beyond the second point, set up
your level between the second point and third point, place the rod at
the second point, then at the third point, and find their difference in
level as above. If the third point is 1 foot above the second, the total
rise in the 200 feet is 2½ feet; if, however, it is 1 foot below the
second, the rise is 1½ minus 1 or ½ foot in the 200 feet.

You can repeat this with as many points as you please.

[Illustration:

  FIG. 64

  A SPIRIT LEVEL
]


Experiment 46. To make a spirit level.

The spirit level (Fig. 64) is simply a curved glass tube filled with
alcohol except for the bubble and closed at both ends. The curve of the
tube is part of a circle.

[Illustration:

  FIG. 65

  MAKING A SPIRIT LEVEL
]

Make a spirit level as follows: Take a piece of No. 4 tube about 7
inches long, heat a space about 3 inches long in the lamp flame, turn
constantly, and when soft remove from the flame, hold both ends and
allow the center to sink into a slight curve (1, Fig. 65).

Let the tube cool, mark the center of the curve with ink, and make marks
2 inches from the center on each side.

Hold the tube crosswise in the lamp flame, heat at one mark, draw down
the tube and close it (2).

In a similar manner draw down the tube at the other mark but do not
close it (3).

Let the tube cool and fill it with alcohol to the level shown in 4. To
do this easily make the pipette (5), suck alcohol into it within about 1
inch of the top, put your finger over the top, insert the lower end of
the pipette to the bottom of 4, and remove your finger.

[Illustration:

  FIG. 66

  MOUNTING THE SPIRIT LEVEL
]

Heat the small part of 4, without heating the alcohol, and close the
tube (6). Now attach the level to a smooth board as 2 or 3, Fig. 66,
mark the center of the bubble, and your spirit level is ready for use.


Experiment 47. To make a fountain-pen filler.

Attach a rubber coupling to the large end of one of your No. 4 nozzles,
close the other end of the coupling with a glass plug, and your
fountain-pen filler is made (Fig. 67).

To make the plug, close one end of a piece of No. 4 tubing, allow it to
cool, cut off to a length of 1 inch and smooth the rough edges. Insert
the closed end of this plug into the rubber coupling.

Practice using the filler by drawing up and shooting out water.

[Illustration:

  FIG. 67

  A FOUNTAIN-PEN FILLER
]


Experiment 48. To make a syringe.

Take a half length of No. 6 tube and smooth both ends in the lamp flame
or blowpipe flame.

Now to make a plunger: Cut an 8½-inch length of No. 2. smooth one end,
close the other end and blow a slight bulb. When cold, wet the closed
end and insert it into a small wet rubber coupling.

=Note=: Always grasp a tube near the end when you insert it into a
coupling or stopper, because if you hold it too far back you may break
it. Insert it with a twisting motion, after wetting the end and the
inside of the coupling or stopper.

[Illustration:

  FIG. 68

  A SYRINGE
]

Wet the inside of the large tube, wet the plunger and rub it on a cake
of soap to make it slippery, then try it in the large tube. If the
plunger is too large, stretch the coupling lengthwise; if it is too
small, crowd the coupling together lengthwise. If the bulb is too large
or too small, dry it, heat in the blowpipe flame until it shrinks, and
blow another.

When the plunger is made, attach a No. 4 nozzle to the No. 6 tube with a
large coupling, arrange as in Fig. 68, and your syringe is made.

Fill the large tube with water and see how long a stream you can make.

[Illustration:

  FIG. 69

  ANOTHER SYRINGE
]


Experiment 49. To make another syringe.

Heat a piece of No. 6 in the blowpipe flame at a length of 7½ inches and
draw it out into a nozzle; smooth the other end in the lamp flame. Use
the same plunger as in Experiment 48, and your syringe is made (Fig.
69). Try it out with water.


Experiment 50. To make a third syringe.

Heat a piece of No. 6 tube in the blowpipe flame at a length of 7½
inches, draw it out, and close the end, then smooth the other end.

Now to make a plunger: Heat a piece of No. 2 tube 8½ inches from one end
in the lamp flame, draw it out into a nozzle, and break it off, leaving
a small hole at the end of the nozzle. Smooth the other end in the lamp
flame, flare it out slightly, allow it to cool, dip it into water and
insert it into a small wet coupling.

[Illustration:

  FIG. 70

  A THIRD SYRINGE
]

Now fill the large tube with water and insert the coupling plunger (Fig.
70). Do you get a fine long stream?


Experiment 51. To make a diablo whistle.

Use the No. 6 tube and the No. 2 plunger from Experiment 48, arrange as
in Fig. 71, blow across the top, and move the plunger up and down. Do
you get a most diabolical sound?

[Illustration:

  FIG. 71

  THE DIABLO WHISTLE
]

The sound is produced by the vibration of the air column between the top
of the tube and the top of the plunger. Do you find that the pitch of
the note is higher the shorter the air column?


Experiment 52. Fun with the diablo whistle.

Start with the air column long and blow the note, shorten it a little
and blow the next note, continue, and try to blow the eight notes of an
octave.

[Illustration:

  FIG. 72

  JOINING TWO TUBES
]

Try to play a tune.

Try to make the most weird sound you can.


Experiment 53. To join two tubes end to end.

Take a piece of No. 2 tube about 7 inches long, close one end, smooth
the other, and when cool cut the tube at the middle.

[Illustration:

  FIG. 73

  WORKING THE JOINT
]

Now join these two pieces as follows: Hold the ends opposite each other
near the top of the lamp flame (Fig. 72), rotate constantly, and when
nearly red hot bring the ends accurately together in the flame, press
together slightly, draw out slightly, and remove from the flame.

The ends are now stuck together, but the glass is in a slight lump
around the joint and if allowed to cool will crack very easily. It is
necessary to work the glass back and forth to get rid of the lump and to
make the glass uniform on both sides of the joint. Do this as follows:
Heat one third of the joint in the blowpipe flame (Fig. 73), and when
red hot blow a slight bulge. Now turn the joint one third, heat the next
third red hot and blow a slight bulge. Repeat with the remaining third.

[Illustration:

  FIG. 74

  JOINING TUBES OF DIFFERENT SIZES
]

Now heat the first third again until it is red hot and shrinks, then
blow a slight bulge again. Repeat this with the other two thirds.

Repeat this whole operation a third time and blow just enough to leave
the joint the same size as the remainder of the tube or a little larger.

[Illustration:

  FIG. 75

  MAKING A LARGE HOLE
]

This heating and blowing has worked the joint back and forth until the
glass is fairly uniform. It makes a strong joint.

Cut off the closed end and smooth the edge.

Repeat with a piece of No. 4 tube.

[Illustration:

  FIG. 76

  MAKING A TEE
]


Experiment 54. To join tubes of different sizes.

Take a piece of No. 4 tubing about 3 inches long and close one end.

[Illustration:

  FIG. 77

  THREE-ARMED SIPHON
]

Take a piece of No. 6 tubing, attach a handle to one end, heat the No. 6
tube in the blowpipe flame about 1 inch from this end and draw it down
to smaller size.

Break the small part at a point where it is about the size of the No. 4
tube. If the hole is too large, heat the edge until it is a little too
small and flare it out with the flaring tool. If the hole is too small,
heat the edge and flare it out.

Now heat the ends of both tubes (Fig. 74), and join them as described in
the last experiment.

Repeat the operation of heating and blowing at least three times.

Join a No. 4 and a No. 2 tube in the same way.


Experiment 55. To make a large hole.

Take a piece of No. 4 tube about 6 inches long, close one end, smooth
the other, and allow it to cool.

[Illustration:

  FIG. 78

  A REPEATING AIR GUN
]

Now to make a large hole in the side of this tube, proceed as follows:
Heat in the blowpipe flame the point at which you wish to make the hole,
and blow a slight bulge (1, Fig. 75). Then heat the top of this bulge
until it is red hot over an area about equal to the size of the hole you
wish to make, and blow hard to make a thin bubble (2, Fig. 75). Break
away the thin glass of the bubble, smooth the edges, and the hole is
made. The edge of this hole will project beyond the side of the tube (3,
Fig. 75). If you wish to make the edge even with the side of the tube,
heat it in the blowpipe flame until it shrinks back level with the tube.

[Illustration:

  FIG. 79

  FOUR-WAY JUNCTION
]


Experiment 56. To make a tee.

Take a piece of No. 4 tube about 6 inches long, close one end, smooth
the other, and allow it to cool. Take another piece 3 inches long, close
one end, and allow it to cool.

Now make a hole in the side of the first tube at a point 3 inches from
the closed end. Do this as described in the last experiment but leave
the hole projecting beyond the side of the tube (1, Fig. 76).

[Illustration:

  FIG. 80

  MAKING A Y
]

Now heat the edge of the hole and the end of the short piece in the lamp
flame, and make a joint (2, Fig. 76) exactly as described in Experiment
53. Be particular to heat and blow all around the joint at least three
times to make the glass uniform, and on the last blowing leave the joint
a little larger than the tube. Cut off the closed ends, make the arms
equal in length, smooth the ends, and your tee is made (3, Fig. 76).

Your first attempt may not be beautiful, but if you will repeat the
heating and gentle blowing often enough, the joint will be strong, which
is the main point.

Repeat until you can make a tee easily.

Make a tee with No. 2 tubing.

Your flame is hardly large enough to make a tee with No. 6 tubing.


Experiment 57. A three-armed siphon.

Make a three-armed siphon as shown in Fig. 77. Put two arms in tumblers
filled with water, suck air out of the third arm until the water runs,
and then put it in an empty tumbler.

Stand the three tumblers on the table. Does the water run until the
levels are the same?

Put one tumbler on a book. Does the water run into the other two
tumblers until the levels are the same?

Return the one tumbler to the table and put the other two on the book.
Does the water run from both tumblers to the lower tumbler until the
levels are again the same?


Experiment 58. To make a repeating air gun.

[Illustration:

  FIG. 81

  BALANCING COLUMNS
]

Take a full length of No. 4 tubing, put a branch about 3 inches long at
a point about 2 inches from one end; leave the end of the branch closed
(Fig. 78). Now load the branch with shot or coarse dry sand, and your
repeating air gun is ready for use.

Tilt the branch slightly above the horizontal and blow intermittently.
Does your gun reload after each blow, until the ammunition is used up?


Experiment 59. To make a four-way junction.

Make a tee as in Experiment 56, but do not cut off the closed ends. Now
attach a fourth arm, as in Fig. 79, and heat and blow gently as before
to work the glass into uniform condition. Cut off the closed arms at
equal lengths, smooth the ends, and your four-way junction is made.


Experiment 60. A four-arm siphon.

Make a four-arm siphon, repeat the experiments described in Experiment
57, and make others of your own.


Experiment 61. To make a Y.

Make a tee as in Experiment 56, then make a bend about ½ inch from the
stem on each side (Fig. 80), and your Y is complete.


Experiment 62. Balancing columns.

Arrange the apparatus as in Fig. 81, put the arms together in a glass of
water, suck a little air out of the top coupling and close it with a
glass plug. Do you find that the water rises to the same level in each?

Place the arms in separate tumblers filled with water to the same level
and repeat. Does the water rise to the same level?

[Illustration:

  FIG. 82

  THE WATER LEVELS ARE THE SAME
]

Add an extra length to one arm and repeat. Are the levels different but
are they equal distances above the water in their respective tumblers?

Place the tumblers on the table, make one tube slanting, and repeat the
experiment (Fig. 82). Are the levels again the same?

When you suck air out of the tee, you decrease the air pressure in the
two tubes, and the atmospheric pressure on the water in the tumblers
lifts the water into the tubes.


Experiment 63. Unequal columns.

Put a large handful of salt into a tumbler partly filled with water and
stir until the salt is dissolved. Now pour fresh water into another
tumbler until it is at the same height as the salt water. Make the arms
of equal length, put one arm in the salt water and the other in the
fresh water, then suck a little air out of the top coupling and close it
with a plug. Do you find that the column of salt water is shorter than
the column of fresh water (1, Fig. 83)? It is shorter because salt water
is heavier than fresh water.

[Illustration:

  FIG. 83

  UNEQUAL COLUMNS
]

If you have gasoline or kerosene convenient fill one tumbler half full
of either, and the other tumbler half full of water, then repeat the
experiment. Do you find that the column of gasoline or kerosene is
longer than the column of water (2, Fig. 83)? It is longer because
gasoline and kerosene are lighter than water.


Experiment 64. To fuse wire into glass.

Find a piece of thin iron or copper wire about 4 inches long, heat the
end of a piece of No. 2 tubing until it is nearly closed, insert the
iron or copper wire into the small hole, and heat the glass around the
wire until it shrinks and grips the wire firmly (Fig. 84). The glass
then serves as a handle for the wire.

[Illustration:

  FIG. 84

  WIRE FUSED INTO GLASS
]

It is difficult to make a secure joint between iron or copper wire and
glass because they both expand and contract more than glass when heated
and cooled. It is easy to make a secure joint between platinum wire and
glass because platinum and glass expand and contract at practically the
same rate when heated and cooled. Platinum, however, is too expensive to
be used for ordinary experiments.


Experiment 65. To cut window glass.

The common glass cutter is a small very hard steel wheel mounted on a
handle (Fig. 85). Practice with one on a pane of glass: place a ruler on
the glass, draw the wheel along the ruler (Fig. 86) with sufficient
pressure to scratch the glass, place the under side of the scratch
exactly over the edge of the table, and press down on both sides.

[Illustration:

  FIG. 85

  A GLASS CUTTER
]


Experiment 66. To bore a hole in glass.

[Illustration:

  FIG. 86

  CUTTING A PANE OF GLASS
]

Place a piece of window glass flat on the table, pour a little kerosene
on the spot to be bored, clasp the file near the end, press the end down
hard on the spot and turn it back and forth with a gouging motion (Fig.
87). You twist the file just as you would twist an awl to force it into
hard wood.

You will soon penetrate the surface; use plenty of kerosene and continue
the boring until you are nearly through; then turn the plate over and
start a hole on the other side to meet the one you have made.

[Illustration:

  FIG. 87

  BORING A HOLE IN GLASS
]

Do not rush things; it will take you ten or fifteen minutes to bore
through ordinary window glass.

Bore a hole in a bottle in the same way, except that the boring is all
from the outside.

If the end of the file becomes dull, break off a small piece, with a
pair of pliers, to expose a fresh surface.


Experiment 67. To cut a bottle in two.

[Illustration:

  FIG. 88

  BOTTLE READY TO BE CUT IN TWO
]

Wind a strip of blotting-paper or wrapping paper 2 inches wide around
the bottle at one side of the line along which you wish to cut. Make
three or more thicknesses and then tie the paper with cord within ½ inch
of the edge to be cut. Wrap another similar piece on the opposite side
of the place to be cut and ³⁄₁₆ inch from the first piece (Fig. 88).

[Illustration:

  FIG. 89

  HEATING THE BOTTLE
]

Now stand the bottle in a pail of water until the paper is thoroughly
wet (about five minutes), take it out, rotate it in a horizontal
position and direct the blowpipe flame against the glass between the
papers (Fig. 89).

Continue this for four or five minutes, then if the bottle has not
dropped apart, plunge it vertically into the pail of water.

The bottle will break into two parts along the line between the two
papers (Fig. 90). If it does not do so, repeat the operation until it
does. Smooth the rough edges outside and inside with the file. You
cannot do this with the flame because the glass is too brittle.

[Illustration:

  FIG. 90

  THE BOTTLE CUT IN TWO
]


Experiment 68. To grind glass.

Rough edges of glass can be ground smooth by means of emery paper. For
example, to smooth the edges of the glass bottle you have just cut in
two, use the file for the rough work, then lay a piece of emery paper on
a plate of glass, emery side up, pour a little kerosene on it and rub
the rough surface on the emery with a rotary motion (Fig. 91). Finish
with fine emery paper, and smooth the edges inside and out with the fine
paper.

[Illustration:

  FIG. 91

  SMOOTHING THE EDGES
]


Experiment 69. To cement glass.

There are two important points to remember in cementing glass: first, to
get the glass clean, and second, to press the surfaces together after
applying the cement, to squeeze out as much of the cement as possible,
and to keep them pressed together until the cement is hard. To clean the
glass wash it thoroughly with soap and water, rinse, and dry with a
clean cloth.

[Illustration:

  FIG. 92

  CEMENTING GLASS
]

There are many excellent glass cements on the market. Some of these are
solid and are used only on hot glass; others are liquid and are used on
cold or hot glass.

Cement two strips of glass together (Fig. 92) with sealing wax or solid
shellac or some other solid cement as follows: Clean the glass
thoroughly, place in the oven or on the stove, heat gradually until the
glass just melts the cement, rub the cement over both surfaces, bring
them together when the cement is fluid, press them together to squeeze
out as much cement as possible, and keep them pressed together until the
cement is hard.

Cement a strip of wood to a strip of glass in the same way.

Cement a strip of wood to a strip of glass with liquid glue, both wood
and glass being cold. Keep them pressed together until the glue is dry,
perhaps a day or two.


                          MAGICAL EXPERIMENTS

Boys, you can perform many magic experiments with apparatus made out of
the glass tubes, rubber stoppers, and rubber unions supplied with
“Experimental Glass Blowing.” We outline a number in the following
pages. You can invent many more for yourselves.


                           MAGIC WITH FLAMES


Experiment 70. Magic lighting.

Light your alcohol lamp, blow it out, and bring a lighted match down
toward the wick from above (Fig. 93). Does the lamp light in a most
magical manner =before the match touches the wick=?

[Illustration:

  FIG. 93

  MAGIC
]

Repeat this with a kerosene lamp and with a candle. Do they light in the
same magical manner?


                            The “why” of it

When the lamp is lighted, the alcohol or kerosene turns to a gas, and it
is the gas which burns; when the candle is lighted, the wax turns to an
oil, the oil turns to a gas, and it is the gas which burns.

The gas rises from the wick for a short time after the flame is blown
out, and it is this gas which lights when you bring the match down
toward the wick.


Experiment 71. Air used by flames.

[Illustration:

  FIG. 94

  THE CANDLES GO OUT AND THE WATER RISES
]

Drop melted candle wax on a tin can cover and attach the bottoms of two
candles to the cover (Fig. 94); use one candle about 4 inches long and
another about 3 inches, stand them upright in a pan of water, light
them, and invert a wide-mouthed bottle over them. Does some air escape
at first due to expansion, do both candles go out, the taller one first,
and does the water rise until the bottle is about one-fifth full?

[Illustration:

  FIG. 95

  THE CORK RISES
]

Cut a piece of candle ½ inch long, float it on a flat cork or can cover
in the pan of water, light it, and invert a fresh empty bottle over it
(Fig. 95). Is the result similar?


                            The “why” of it

The water rises in the bottle because ⅕ of the air is used up by the
burning candle. Air is ⅕ oxygen and ⅘ nitrogen. The oxygen unites with
the burning gas of the candle and produces water vapor (H_{2}O) and
carbon dioxide (CO_{2}); the nitrogen takes no part in the burning.

[Illustration:

  FIG. 96

  WATER FROM FLAME
]

The water vapor (H_{2}O) condenses to water on cooling and takes up very
little space. The carbon dioxide remains a gas and occupies space, but
this is offset by the volume of the air which escaped at first. The
result is that the volume of gas at the end is about ⅕ less, and the
atmospheric pressure on the water in the pan lifts water into the
bottle.

The candle goes out because it must have oxygen to burn and the oxygen
is used up.


Experiment 72. Water produced by fire.

It is certainly magic to produce water from fire, but you can do it
easily as follows: Hold a clean, dry, cold tumbler over your alcohol
lamp flame (Fig. 96). Does water deposit in the form of mist on the
inside of the tumbler?

[Illustration:

  FIG. 97

  ATMOSPHERIC PRESSURE
]

Repeat with fresh tumblers with the flame of a kerosene lamp and of a
candle. Are the results similar?

Direct the blowpipe flame into the end of a piece of No. 2 or 4 tubing.
Does water deposit in drops inside the tube about 1 inch above the end?


                            The “why” of it

One of the chief constituents of alcohol, kerosene, and candle wax is
hydrogen (H), and when this burns in the oxygen (O) of the air, it
produces water (H_{2}O). It is this water which condenses on the cold
glass.


                             MAGIC WITH AIR


Experiment 73. Atmospheric pressure.

Arrange a No. 6 tube as in 1, Fig. 97, and suck air out at the top. Does
the water run uphill into your mouth?

Hold your finger over the top and lift the tube out of the pail (2).
Does the water remain in the tube? Fill a bottle with water to
overflowing, insert a No. 2 tube into your one-hole stopper, insert the
stopper into the mouth of the bottle (3) without admitting air below the
stopper, and try to suck water out of the bottle. Do you find that you
cannot do so?

[Illustration:

  FIG. 98

  WATER DRIVEN UP TUBE BY ATMOSPHERE
]

Repeat (3) with the bottle half full of air (4). Do you find that you
can now suck part of the water out of the bottle, and all of it if you
admit air?


                            The “why” of it

The atmosphere which surrounds the earth exerts a pressure of 15 pounds
per square inch on everything at the earth’s surface. It exerts this
pressure equally downward, sidewise, and upward.

It is this atmospheric pressure on the water in the pail (1) which lifts
the water into the tube when you decrease the pressure on the water in
the tube by sucking out air and then water.

It is this pressure upward that supports the water in 2.

The water does not rise in 3 because the atmosphere cannot exert
pressure downward on the water in the bottle.

[Illustration:

  FIG. 99

  A FOUNTAIN
]

The rise of the water in 4 is due to another fact, namely, that any gas
expands when the pressure on it is decreased. When you suck air out of
the tube you decrease the pressure on the water in the tube and thereby
on the air in the bottle; the air then expands and lifts the water into
your mouth.


Experiment 74. Great pressure of air.

With the apparatus Fig. 98 hold your finger over the lower end of the
tube, suck as much air as you can out of the tube, pinch the coupling,
and remove your finger under water. Does the atmosphere drive water up
the tube very rapidly and with great force?

[Illustration:

  FIG. 100

  MAGIC
]


Experiment 75. A fountain.

With the apparatus Fig. 99 suck as much air as you can out of the
bottle, pinch the coupling, and open it under water. Does the atmosphere
lift the water into the bottle and produce a beautiful fountain?

[Illustration:

  FIG. 101

  MORE MAGIC
]


Experiment 76. Magic tumbler.

Fill a tumbler with water, cover it with a sheet of paper, hold the
paper on with your hand, invert the tumbler, and remove your hand (Fig.
100). Does the atmospheric pressure upward support the paper and water?


Experiment 77. Magic lift.

Fill a tumbler with water, press your palm down on the top with your
fingers pointing downward (Fig. 101), straighten your fingers without
admitting air to the tumbler, and then lift your hand. Do you lift the
tumbler of water also?

There is a partial vacuum between your hand and the water, and the
atmospheric pressure upward and downward holds your hand and the tumbler
together.

[Illustration:

  FIG. 102

  TUMBLER PENDULUM
]


Experiment 78. A magic pendulum.

Pass a string through a small hole in a piece of cardboard, knot the end
of the string, and drop melted candle wax over the hole to make it air
tight.

Fill a tumbler with water, press the cardboard down on the tumbler with
the palm of your hand, and lift the string. Do you also lift the tumbler
(Fig. 102)?

Swing the tumbler gently as a pendulum.

[Illustration:

  FIG. 103

  POULTRY FOUNTAIN
]


Experiment 79. A poultry fountain.

To make the poultry fountain (Fig. 103), fill a bottle with water, hold
your thumb over the mouth, invert the bottle over the pan of water, and
remove your thumb under water. Does the atmospheric pressure on the
water in the pan hold the water in the bottle?

Lift the bottle until the mouth is a little above the water in the pan.
Does air enter and water run out until the mouth is again covered with
water? This is what happens when the poultry, by drinking, lower the
water below the mouth of the bottle.

In a poultry fountain the bottle is supported, as shown, with its mouth
under water but above the bottom.

[Illustration:

  FIG. 104

  A DRINKING FOUNTAIN

  (_From Butler’s Household Physics. Published by Whitcomb & Barrows,
    Boston_)
]

[Illustration:

  FIG. 105

  HOMEMADE DRINKING FOUNTAIN
]


Experiment 80. A drinking fountain.

The drinking fountain (Fig. 104) is similar in principle to the poultry
fountain of the last experiment. The water is held in the large inverted
bottle by the atmospheric pressure on the water in the lower vessel. Air
enters the bottle and water escapes from it when the level of the water
in the lower vessel falls below the mouth of the bottle. The water is
cooled by the ice surrounding the lower vessel.

Make a drinking fountain of this kind as in Fig. 105, ask a friend to
hold it, remove the glass plug from the coupling, and draw a glass of
water. Do you observe that air bubbles enter the inverted bottle and
water flows from it only when the water level in the half bottle falls
below the mouth of the inverted bottle?

Allow the water to flow continuously. Is the water level practically
constant in the half bottle until the upper bottle is empty?

------------------------------------------------------------------------




                          TRANSCRIBER’S NOTES


 ● Typos fixed; non-standard spelling and dialect retained.
 ● Enclosed italics font in _underscores_.
 ● Enclosed bold font in =equals=.
 ● Subscripts are shown using an underscore (_) with curly braces { },
     as in H_{2}O.



*** END OF THE PROJECT GUTENBERG EBOOK 73841 ***