how ball fountain floats on water

 Granite sphere /stone ball/marble sphere

1. Even though the ball weighs a 30 KG to 30000 KG, even a small 
child can change the course of it and send it into an accelerated 
spin. There are no belts, pulleys or wheels used to make the
ball spin. It is floating on water. 
2. The sphere/ball made two key elements: the ball itself and
the base  it sits in. Cutting these two is a very complicated
process as any large differences between the contours of
them will prevent the ball from turning properly or sitting
in the socket. The two pieces are machined at the same
time to ensure any differences between them are minute.
When finished and the ball is placed in the socket, the
space between the two will be less than the thickness
of a business card. 
What to do: See if you can spin half a ton of granite!
What happens: You can spin the granite ball because it is floating
on water. The water pressure is only about 3 pounds per square inch
in the gap between the ball and the cup. There are enough square
inches for this pressure to hold up to 1200 pounds of granite!
3. The sphere/ball/globe is made from granite/marble/hard rocks, a type of igneous rock. The word ‘igneous’ means ‘made
from fire or heat’. Granite forms when molten rock (known as magma) below the surface
of the Earth cools very slowly. As it cools, the magma turns into solid rock. The
granite contains coarse grains of crystals, such as quartz. It is its appearance
that gives granite its names, as it comes from the Latin for ‘grainy’. Granite
forms a large part of the continental crust and can be found in many
mountainous regions around the world. Because it is so hardwearing
and tough, granite is widely used in construction.
4. Water is pumped up from beneath the socket. This
lubricates the sphere and puts pressure on it, forcing it to turn
gently. Once the ball has begun to revolve, it will continue to
do so until the water is shut off. 
5. The pressure of the pump in this exhibit
is very very low, at 3 pounds per square
inch (psi). Other large spheres operate at higher
pressures, between 14 and 21 psi. This is in
comparison to, for example, tyre pressure, 
which can be between 26 and 34 psi. if you want to buy just email on