Calehill, Kent.
{295}
_Curious Fact in Natural Philosophy_ (Vol. vii., p. 206.).--In Young's
_Natural Philosophy_ it is said, that if the cup of a barometer is placed
in a vessel somewhat larger than the cup, so contrived that the tube of the
barometer may fit air-tight in the top of the vessel, and if two holes are
made in the vessel on opposite sides, a current of air driven in at one
hole will cause the mercury to fall. Is not the case of the cards analogous
to this? and might not the cause be, that the current of air carries away
with it some of that contained between the cards, and so that the air is
sufficiently rarefied to cause a pressure upwards greater than that caused
by the current downwards, and the effect of gravity? Might not the sudden
fall of the barometer before storms be from a cause similar in some degree
to this?