jorcans and the adventurous Moors, were followers of almost equal
temerity.

A knowledge of the variation of the needle came more slowly to be known
to the mariners of the Mediterranean. It had been observed by Peregrini
as early as 1269, but that knowledge of it which rendered it greatly
serviceable in voyages does not seem to be plainly indicated in any of
the charts of these transition centuries, till we find it laid down on
the maps of Andrea Bianco in 1436.

It was no new thing then when Columbus, as he sailed westward, marked
the variation, proceeding from the northeast more and more westerly; but
it was a revelation when he came to a position where the magnetic north
and the north star stood in conjunction, as they did on this 13th of
September, 1492. As he still moved westerly the magnetic line was found
to move farther and farther away from the pole as it had before the 13th
approached it. To an observer of Columbus's quick perceptions, there was
a ready guess to possess his mind. This inference was that this line of
no variation was a meridian line, and that divergence from it east and
west might have a regularity which would be found to furnish a method of
ascertaining longitude far easier and surer than tables or water clocks.
We know that four years later he tried to sail his ship on observations
of this kind. The same idea seems to have occurred to Sebastian Cabot,
when a little afterwards he approached and passed in a higher latitude,
what he supposed to be the meridian of no variation. Humboldt is
inclined to believe that the possibility of such a method of
ascertaining longitude was that uncommunicable secret, which Sebastian
Cabot many years later hinted at on his death-bed.

The claim was made near a century later by Livio Sanuto in his
_Geographia_, published at Venice, in 1588, that Sebastian Cabot had
been the first to observe this variation, and had explained it to
Edward VI., and that he had on a chart placed the line of no variation
at a point one hundred and ten miles west of the island of Flores in the
Azores.

These observations of Columbus and Cabot were not wholly accepted during
the sixteenth century. Robert Hues, in 1592, a hundred years later,
tells us that Medina, the Spanish grand pilot, was not disinclined to
believe that mariners saw more in it than really existed and that they
found it a convenient way to excuse their own blunders. Nonius was
credited with saying that it simply