How a submarine is raised and lowered
Place pieces of iron or rocks in the bottom of a small wide-mouth bottle and pour a little
melted paraffin on them to fasten them down so that the bottle will float in an upright
position. Insert a two-hole stopper. In one hole place a U-shaped length of glass tubing
which extends to the bottom of the bottle. In the
other hole put a short length of glass tube and a
rubber tube. Set the bottle in a large vessel of
water.
Withdraw some air by sucking on the rubber tube
and water will siphon into the bottle until the
bottle sinks. The bottle may be made to rise by
blowing out part of the water.
Actually, submarine engineers adjust the
buoyancy of the submarine to that of the water
and then use the elevators to dive or climb. To
remain at the surface they will 'blow' the tanks
with surface air after rising. The use of compressed air to empty the tanks is not
practical while the submarine is submerged. The device also illustrates the principle of
the tanks or pontoons used to lift sunken ships. Fasten a weight to the bottle, sink
both in water and lift the weight by blowing air into the bottle.