order, and for all the elaborate discipline of sea life to be arranged
and established; and we may employ the interval by noting what aids to
navigation Columbus had at his disposal.


The chief instrument was the astrolabe, which was an improvement on the
primitive quadrant then in use for taking the altitude of the sun. The
astrolabe, it will be remembered, had been greatly improved, by Martin
Behaim and the Portuguese Commission in 1840--[1440 D.W.]; and it was
this instrument, a simplification of the astrolabe used in astronomy
ashore, that Columbus chiefly used in getting his solar altitudes. As
will be seen from the illustration, its broad principle was that of a
metal circle with a graduated circumference and two arms pivoted in the
centre. It was made as heavy as possible; and in using it the observer
sat on deck with his back against the mainmast and with his left hand
held up the instrument by the ring at the top. The long arm was moved
round until the two sights fixed upon it were on with the sun. The point
where the other arm then cut the circle gave the altitude. In
conjunction with this instrument were used the tables of solar
declination compiled by Regiomontanus, and covering the sun's declination
between the years 1475 and 1566.

The compass in Columbus's day existed, so far as all essentials are
concerned, as it exists to-day. Although it lacked the refinements
introduced by Lord Kelvin it was swung in double-cradles, and had the
thirty-two points painted upon a card. The discovery of the compass, and
even of the lodestone, are things wrapt in obscurity; but the lodestone
had been known since at least the eleventh century, and the compass
certainly since the thirteenth. With the compass were used the sea
charts, which were simply maps on a rather larger and more exact scale