One of them, indeed, which he kept
by him for his own use, and constantly compared with a fixed
star, did not vary so much as one whole minute during the ten
years that he continued in the country after finishing the
machine.[6]
Living, as he did, not far from the sea, Harrison next
endeavoured to arrange his timekeeper for purposes of navigation.
He tried his clock in a vessel belonging to Barton-on-Humber; but
his compensating pendulum could there be of comparatively little
use; for it was liable to be tossed hither or thither by the
sudden motions of the ship. He found it necessary, therefore, to
mount a chronometer, or portable timekeeper, which might be taken
from place to place, and subjected to the violent and irregular
motion of a ship at sea, without affecting its rate of going. It
was evident to him that the first mover must be changed from a
weight and pendulum to a spring wound up and a compensating
balance.
He now applied his genius in this direction. After pondering
over the subject, he proceeded to London in 1728, and exhibited
his drawings to Dr. Halley, then Astronomer-Royal. The Doctor
referred him to Mr. George Graham, the distinguished horologer,
inventor of the dead-beat escapement and the mercurial pendulum.
After examining the drawings and holding some converse with
Harrison, Graham perceived him to be a man of uncommon merit, and
gave him every encouragement.
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