408 FIRST REPORT UPON MAGNETIC WORK

This line lay a little to the west of Fayal Island of the Azores. ¹ It
will be remembered that this line figured quite prominently for many
years in political geography as the line of demarcation between the
kingdoms of Portugal and Castile.

It is only lately that Columbus has been properly credited with this
discovery. Generally he is given credit merely for the discovery of
the line of no decimation. This is due to an error made by an Italian,
Formaleoni, who declared that the compass charts in Bianco's famous
atlas of 1436 contained on them values of the magnetic declination.
Humboldt, relying on Formaleoni, repeated the error in his " Cosmos. "
Later researches have shown beyond a doubt that Formaleoni was
wrong, having misinterpreted a diagram on one of the charts. So
likewise has it been conclusively proven that the value of 5° E. for
the magnetic declination at Rome in 1269, which had been ascribed
to one Petrus Peregrinus, had been inserted in the Leyden manuscript
in the early part of the sixteenth century.

An examination of the early compass charts made by the writer
would indicate that during Columbus' time and a century or two be-
fore, the needle pointed approximately to the true north or by a small
amount east over the entire Mediterranean. For this reason, probably,
the magnetic declination was not discovered for so long a time after
the European mariner had begun to rely on the bit of magnetized
steel to guide the wanderings of his ship. Frequently statements are
seen, with deductions based on them, that the needle pointed by a
large amount (15°-20° and more) west in the Mediterranean in about
the 14th or 15th century. This, however, cannot be the case.

It was not until near the middle of the sixteenth century that the f act
of the " misdirection " of the needle—to translate literally the German
word, missweisung, for magnetic declination—received general accept-
ance. It was believed, namely, that the needle's deviation from the
true north was due to mechanical imperfections, and the compasses of

¹ According to Mr. Schott's computations, the place on Columbus' voyage
where the needle pointed true north was in north latitude 28° 2l' and in
longitude 29° 16' west of Greenwich. —Coast and Geodetic Survey Report for
1888, Appendix 7, p. 305. '