provided
with instruments, and not very skilful in their application. The hope of
an accurate clock or time-keeper is more specious. But when I began
these studies, no movements had yet been made that were not evidently
unaccurate and uncertain: and even of the mechanical labours which I now
hear so loudly celebrated, when I consider the obstruction of movements
by friction, the waste of their parts by attrition, the various pressure
of the atmosphere, the effects of different effluvia upon metals, the
power of heat and cold upon all matter, the changes of gravitation and
the hazard of concussion, I cannot but fear that they will supply the
world with another instance of fruitless ingenuity, though, I hope, they
will not leave upon this country the reproach of unrewarded diligence. I
saw, therefore, nothing on which I could fix with probability of
success, but the magnetical needle, an instrument easily portable, and
little subject to accidental injuries, with which the sailor has had a
long acquaintance, which he will willingly study, and can easily
consult. The magnetick needle, from the year 1300, when it is generally
supposed to have been first applied by Flavio Gioia, of Amalfi, to the
seaman's use, seems to have been long thought to point exactly to the
north and south by the navigators of those times; who sailing commonly
on the calm Mediterranean, or making only short voyages, had no need of
very accurate observations; and who, if they ever transiently observed
any deviations from the meridian, either ascribed them to some
extrinsick and accidental cause, or willingly neglected what it was not
necessary to understand.

But when the discovery of the new world turned the attention of mankind
upon the naval sciences, and long courses required greater niceties of
practice, the variation of the needle soon became observable, and was
recorded, in 1500, by Sebastian Cabot, a Portuguese, who, at the expense
of the king of England, discovered the northern coasts of America.

As the next century was a time of naval adventures, it might be expected
that the variation once observed, should have been well studied: yet it
seems to have been little heeded; for it was supposed to be constant,
and always the same in the same place, till, in 1625, Gellibrand noted
its changes, and published his observations.

From this time the philosophical world had a new subject of speculation,
and the students of magnetism employed their r