esearches upon the gradual
changes of the needle's direction, or the variations of the variation,
which have hitherto appeared so desultory and capricious, as to elude
all the schemes which the most fanciful of the philosophical dreamers
could devise for its explication. Any system that could have united
these tormenting diversities, they seem inclined to have received, and
would have contentedly numbered the revolutions of a central magnet,
with very little concern about its existence, could they have assigned
it any motion, or vicissitude of motions, which would have corresponded
with the changes of the needle.

Yet upon this secret property of magnetism I ventured to build my hopes
of ascertaining the longitude at sea. I found it undeniably certain that
the needle varies its direction in a course eastward or westward between
any assignable parallels of latitude: and, supposing nature to be in
this, as in all other operations, uniform and consistent, I doubted not
but the variation proceeded in some established method, though, perhaps,
too abstruse and complicated for human comprehension.

This difficulty, however, was to be encountered; and by close and steady
perseverance of attention I at last subdued, or thought myself to have
subdued it: having formed a regular system in which all the phenomena
seemed to be reconciled; and, being able, from the variation in places
where it is known, to trace it to those where it is unknown; or from the
past to predict the future; and, consequently, knowing the latitude and
variation, to assign the true longitude of any place.

With this system I came to London, where, having laid my proposals
before a number of ingenious gentlemen, it was agreed that during the
time required to the completion of my experiments, I should be supported
by a joint subscription to be repaid out of the reward, to which they
concluded me entitled. Among the subscribers, was Mr. Rowley, the
memorable constructor of the orrery; and among my favourers was the lord
Piesley, a title not unknown among magnetical philosophers. I frequently
showed, upon a globe of brass, experiments by which my system was
confirmed, at the house of Mr. Rowley, where the learned and curious of
that time generally assembled.

At this time great expectations were raised by Mr. Whiston, of
ascertaining the longitude by the inclination of the needle, which he
supposed to increase or diminish regularly. With this learned man I had