"PrecisionmachinisT" fired this
volley in :

http://en.wikipedia.org/wiki/Pascal%27s_law

PT, you seem to be implying that the pressure will be equal in both parts
of the air amplifier because they are both connected to the source supply
-- which would be the case, if the prior were the case.

But the source only serves to fill the smaller cylinder when it is fully
retracted. It possesses a check valve so that as soon as its pressure
rises above supply, it's cut off from that source, and free to build
pressure to whatever level the ratio of areas between it and the
'driving' cylinder allow.

LLoyd