asis of manner
with which the tongue conveys whatever deeply interests the mind. His 'My
Charlotte!' is affecting; he does not pronounce it as 'Me Charlotte,' but
very simply and evenly, '_My_ Charlotte.'"

* * * * *

NOTES OF A READER.

KNOWLEDGE FOR THE PEOPLE.

Part VII.--_Mechanics._

We quote a few articles from the Introductory portion, illustrating the
general principles of Mechanical agencies.

Why are we said to know of nothing which is absolutely at rest?

Because the earth is whirling round its axis, and round the sun; the sun is
moving round his axis, and round the centre of gravity of the solar system;
and, doubtless, round some more remote centre in the great universe,
carrying all his planets and comets about his path. One of the grand laws
of nature is, that all bodies persevere in their present state, whether of
motion or rest, unless disturbed by some foreign power. Motion, therefore,
once began, would be continued for ever, were it to meet with no
interruption from external causes, such as the power of gravity, the
resistance of the medium, &c. Dr. Arnott adduces several familiar
illustrations of motions and forces. Thus, all falling and pressing bodies
exhibit _attraction_ in its simplest form. _Repulsion_ is instanced in
explosion, steam, the action of springs, &c. Explosion of gunpowder is
repulsion among the particles when assuming the form of air. Steam, by the
repulsion among its particles, moves the piston of the steam-engine. All
elasticity, as seen in springs, collision, &c. belongs chiefly to
repulsion. A spring is often, as it were, a reservoir of force, kept ready
charged for a purpose; as when a gun-lock is cocked, a watch wound up, &c.

Why does a billiard ball stop when it strikes directly another ball of
equal size, and the second ball proceed with the whole velocity which the
first had?

Because the action which imparts the new motion is equal to the re-action
which destroys the old. Although the transference of motion, in such a
case, seems to be instantaneous, the change is really progressive, and is
as follows:--The approaching ball, at a certain point of time, has just
given half of its motion to the other equal ball; and if both were of soft
clay, they would then proceed together with half the original velocity;
but, as they are elastic, the touching parts at the moment supposed, are
compressed like a spring between the balls;