s, it has commonly been accredited
to the Devil? The case of Dr. Faustus is the most familiar
example.]

[Footnote 375: This version is cited from Major's _Prince Henry
the Navigator_, p. 58.]

[Sidenote: Latitude and longitude.]

That time was after all not so long in arriving, for by the end of the
thirteenth century the compass had come to be quite generally used,[376]
and the direction of a ship's course could be watched continuously in
foul and fair weather alike. For taking the sun's altitude rude
astrolabes and jack-staffs were in use, very crazy affairs as compared
with the modern quadrant, but sufficiently accurate to enable a
well-trained observer, in calculating his latitude, to get somewhere
within two or three degrees of the truth. In calculating longitude the
error was apt to be much greater, for in the absence of chronometers
there were no accurate means for marking differences in time. It was
necessary to depend upon the dead-reckoning, and the custom was first to
sail due north or south to the parallel of the place of destination and
then to turn at right angles and sail due east or west. Errors of eight
or even ten degrees were not uncommon. Thus at the end of a long outward
voyage the ship might find itself a hundred miles or more to the north
or south, and six or seven hundred miles to the east or west, of the
point at which it had been aimed. Under all these difficulties, the
approximations made to correct sailing by the most skilful mariners were
sometimes wonderful. Doubtless this very poverty of resources served to
sharpen their watchful sagacity.[377] To sail the seas was in those days
a task requiring high mental equipment; it was no work for your
commonplace skipper. Human faculty was taxed to its utmost, and human
courage has never been more grandly displayed than by the glorious
sailors of the fifteenth and sixteenth centuries.

[Footnote 376: Huellmann, _Staedtewesen des Mittelalters_, bd. i.
pp. 125-137.]

[Footnote 377: Compare the remarks of Mr. Clark Russell on the
mariners of the seventeenth century, in his _William Dampier_,
p. 12.]

* * * * *

[Sidenote: Prince Henry the Navigator, 1394-1463.]

[Sidenote: His idea of an ocean route to the Indies, and what it might
bring.]

We are now prepared to appreciate the character of the work that was
done in the course of