The
hydrostatic weight or differential volume problem
A too prevalent
belief at the present time that a large area or body of water has a
greater hydrostatic pressure than a connected tube rising from its
base. A projector thought that the vessel of his contrivance,
represented here, was to solve the renowned problem of the perpetual
motion. It was goblet-shaped, lessening gradually toward the bottom
until it became a tube, bent upward at c, and pointing with an open
extremity into the goblet again.

He reasoned
thus: A pint of water in the goblet, a,
must more than
counterbalance an ounce which the tube, b, will contain, and must
therefore be constantly pushing the ounce forward into the vessel again
at a, and keeping up a stream or circulation which will cease only when
the water dries up. He was confounded when a trial showed him the same
level in a and in b.
(Subsection 960, from p.385)
From: Gardner D. Hiscox, M.E., Mechanical Appliances and Novelties of Construction (1927), Norman W. Henley Publ. Co.

In science it often happens that scientists say, 'You know that's a really good argument; my position is mistaken,' and then they would actually change their minds and you never hear that old view from them again. They really do it. It doesn't happen as often as it should, because scientists are human and change is sometimes painful. But it happens every day. I cannot recall the last time something like that happened in politics or religion. (1987) -- Carl Sagan