Freiburger historische Bestände - digital

— 17 —

consisted of a staff along which a " transom " could be
shifted at right angles. Divisions of equal length were
marked along staff and transom. An observer desirous of
obtaining the altitude of a star, placed one end of the
staff against his right eye and then shifted the transom
until its lower end touched the horizon and the upper end
hit the star. Nuries, however, points out that owing to
the indefiniteness of the horizon at sea, the results could
not be trusted. The instrument was useless for taking
the altitude of the sun, unless the eye was protected by a
coloured glass or the sun was visible only dimly behind
a screen of vapour. It became practically available only
after John Davis had converted it into a back-staff,1 which
enabled the seaman to take his observations with his back
turned to the sun.

$^\-
✓ ■

A Back-Staff.

When Nunes' essay was published, in 1537, the cross-
staff had been placed in the hands of mariners, but in
Behaim's days it was unknown to them. Columbus,
Vasco da Gama, Cabral, Duarte Pacheco Pereira made
use of the astrolabe and quadrant, but never mention a
cross-staff. A. Vespucci, when appointed Piloto mayor
in 1508,2 was instructed to examine the pilots in the use
of the two instruments named. Under these circumstances
we are bound to disbelieve that Behaim made known the
cross-staff to the Portuguese seamen.

The Quadrant.

There are, of course, a few other instruments which a
merchant coming from Nuremberg might have introduced
to the notice of Portuguese astronomers, such as metal
quadrants, and sundials.

The quadrant had been in use among Portuguese
seamen long before the arrival of Behaim among them,
for Diogo Gomez tells us that in 1456 he made use of it

1 Described in 'The Seaman's Secrets' (London, 1607), and 'The
Voyages and Works of J. Davis,' edited for the Hakluyt Society by
Admiral Sir A. Markham (London, 1880). This famed navigator was
a native of Sandridge in Dovonshire. He was killed in 1605 in a fight
with Japanese.

s ' Navarrete Coleccion,' EEL, Dec. 7-9.

in observing the altitude of the Pole Star.1 Our illustration
shows how it is used, and needs no further explanation.
In at least one respect this simple instrument was superior
to the astrolabe, for it enabled the observer to determine

A Quadrant.

the altitude of the sun when seen looming through fog or
thin clouds, which could be only done with the astrolabe
when the luminary shone brightly.

The Nocturnal.

The nocturnal or horometer, an instrument for ascertaining
the hours of the night by observing the Pole Star
and its so-called guardians, was already known to P.
Apianus. P. Nunes thought little of this instrument, and
it does not seem that it was ever used on board ship.4

Sundials.

In the letter which Dr. Monetarius wrote to King
John of Portugal in 1494 he mentions the "quadrant,
cylinder and astrolabe" as instruments likely to guide
Behaim and other mariners in a proposed voyage across
the western ocean. I have dealt already with the quadrant
and the astrolabe. As to the " cylinder," it is nothing but
one of those portable sundials for the manufacture of
which Nuremberg and other German cities were famous in
the fifteenth and sixteenth centuries. The " cylinder," of
which Sebastian Miinster1 gives an illustrated description,

3 ' De prima inventione Guinea' ('Abh. bayr. Ak. d. Wiss.,' Hist. A.,
1845).

* For illustrated descriptions of the nocturnal see G. Fournier, 'Hydro-
graphie,' liv. X., c. 20, ? nd A. Scbiick,' Das Horometer,' in ' Mitt. d. Geogr.
Ges. in Miinchen,' L, 1905, p. 269.

B ' Compositio horologiorum' (Bas., 1531), c.39. S. Mtinster, the famous
author of a ' Cosmographia,' of which 24 editions in German alone were
published in the course of a century, was born at Tngelheim in 1489, and
died at Basel in 1552.

D