esired point was to sail north or
south until they reached the latitude of their port, and then steer east
or west, as the case might be, until they arrived at their destination,
this plan being further complicated by the intrusion of obstacles in the
shape of headlands and what not in the way. But George Saint Leger
happened to be better equipped in this respect than perhaps any other
man of his time; for as has already been mentioned, he was a lad of
ideas, and one of those ideas was that there ought to be some way of
ascertaining the longitude of a ship, if one could but hit upon it; and
further, that such a way having been found, a mariner might fearlessly
venture out of sight of land, remain out of sight of it as long as he
pleased, and go whither he pleased, with the certainty of being able to
find his way back again. Then, with this postulate firmly fixed in his
mind, he had set himself to work in his leisure time to thrash out the
question of accurately determining the longitude of an unknown place in
relation to a known place. He was convinced that the world was round,
globular in shape, although there were many learned men who disputed
this assertion, and he also knew that the world revolved on its own axis
once in twenty-four hours. Also he knew that when the sun, in the
course of its apparent passage round the earth, attained its highest
point in the heavens, it was noon at that place, and his astrolabe
afforded him the means of determining that moment. Then, still
following the train of thought connected with the earth's diurnal
revolution upon its axis whereby the sun was brought to the meridian
every day at noon, he had not much difficulty in reasoning out the fact
that it cannot possibly be noon at any two or more places at the same
moment unless they happen to be situated on the same meridian, or, in
other words, are of the same longitude. From this to the assurance that
the difference in time between any two places was equivalent to the
difference in longitude between them was an easy step, and led naturally
enough to the next, which was that, if he happened to possess a time-
piece showing, say, the time at Plymouth, he could, by comparing this
with the moment of noon somewhere else, as ascertained by his astrolabe,
determine the exact distance of that place east or west of Plymouth.
The rest was easy; he went to a certain watchmaker in London and ordered
the best watch that could be made for mone