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 the No. 4, and in the No. 4. than in the
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?
FIG. 20
WATER RUNS
UP TUBE
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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 will 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 more common kinds of glass are:
Venetian glass, made from sand, soda, and lime; Bohemian glass,
from sand,
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