rately the distance between the point of suspension and the centre of
oscillation, and even of finding that centre; also the variety of
terrestrial attraction, from which cause the motions of the pendulum are
also liable to variation, even in the same latitude. In pursuing his
researches, Capt. Kater discovered that the motions of the pendulum are
affected by the nature of the strata over which it vibrates.

Why is the iron rim of a coach wheel heated before putting on?

Because the expansion of the metal occasioned by the heat, facilitates the
operation of putting on the iron, while the contraction which follows,
brings the joints of the wooden part together; and thus, binding the whole,
gives great strength to the wheel.

Why does a bottle of fresh water, corked and let down 30 or 40 feet into
the sea, often come up again with the water saltish, although the cork be
still in its place?

Because the cork, when far down, is so squeezed as to allow the water to
pass in or out by its sides, but on rising, it resumes its former size.

Why do bubbles rise on a cup of tea when a lump of sugar is dropped into
it?

Because the sugar is porous, and the air which filled its pores then
escapes to the surface of the tea, and the liquid takes its place.

Why is there an opening in the centre of the upper stone of a corn mill?

Because through this opening the grain is admitted and kept turning round
between the stones, and is always tending and travelling outwards, until it
escapes as flour from the circumference.

Why does water remain in a vessel which is placed in a sling and made to
describe a circle?

Because the water, by its inertia of straightness, or centrifugal (or
centre-flying) force, tends more away from the centre of motion towards the
bottom of the vessel, than towards the earth by gravity.

Why does a young quadruped walk much sooner than a child?

Because a body is tottering in proportion to its great altitude and narrow
base. Now, the child has this latter, and learns to walk but slowly,
because of the difficulty, perhaps in ten or twelve months, while the young
of quadrupeds, having a broad supporting base, are able to stand, and even
to move about almost immediately; but it is the noble prerogative of man to
be able to support his towering figure with great firmness, on a very
narrow base, and under constant change of attitude.--_Arnott._

* * * * *

FINE ARTS.