England, by Robert Harris, in 1641, and erected in Inigo Jones's church of
St. Paul, Covent-garden.

Why does the pendulum move faster in proportion as its journey is longer?

Because, in proportion as the arc described is more extended, the steeper
are its beginning and ending; and the more rapidly, therefore, the pendulum
falls down at first, sweeps along the intermediate space, and stops at
last.--_Arnott._

Why is it extremely difficult to ascertain the exact length of the
pendulum?

Because of the various expansion of metals, respecting which no two
pyrometers agree; the changeable nature of the atmosphere; the uncertainty
as to the true level of the sea; the extreme difficulty of measuring
accurately 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.