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have made his famous landfall equally well had he trusted
entirely to his dead reckoning or, like a bird of passage, to
his instinct, for his observed latitudes are woefully out.1
Verily, the Portuguese seamen of that age were better
observers than their Spanish rivals !

The last paragraph in the account given by J. de
Barros seems to refer to improved tables of the sun's
declination. Dr. Breusing2 suggests, however, that the
author refers to an instrument which superseded the
astrolabe for taking a meridian altitude of the sun on
ship-board, and that this instrument was the cross-staff.
I shall deal fully with this new aid to navigation, and
merely observe in this place that the cross-staff was
known in Portugal when J. de Barros wrote, in 1539,
but that it was not made use of by Vasco da Gama,
Magellan or any other seamen of the period with which
I deal.

Of the three persons named by J. de Barros as
members of the Junta, two, namely Dr. Rodrigo and
Josepe or Jose, have already been referred to, whilst the
third, Martin Behaim, shall be dealt with fully a little
further on.

The Astronomical Expedition of Jose" Vizinho, 1485.

Josepe or Jose Vizinho seems to have taken the lead
in the work done by this Junta. He was no mere
theorist, for we learn from a note inscribed by Christopher
Columbus on a margin of the «Historia Papae Pii'
(Venice, 1477) that in 1485 he was sent to the Guinea
coast for the express purpose of determining a number of
latitudes by observing meridian altitudes of the sun.
This note reads as follows:3

" In the year 1485 the King of Portugal sent Master
Jhosepius, his physician and astrologer, to determine the
altitudes of the sun throughout Guinea, all of which he
performed; and he reported to said most serene king, I
being present, that .... on March ll,4 he found that
the island of idols near Sierra Leone was exactly 5 degrees
distant from the Equator, and he attended to this with
the utmost diligence. Afterwards said most serene king
often sent to Guinea and other places .... and he
always found the results to accord with said Martin
Josepius, whereby I have the certainty that the Castle of
the Mine is under the Equator."

1 He places his landfall (Guanahani), by dead reckoning in 28° N., the
north coast of Cuba, by observation, in 42° N., the true latitudes being
24° and 23° ! On the chart of Juan de la Cosa, his pilot, Trinidad lies in
latitude 14° N., Guadaloupe in 21° N., Guanahani in 35° N., and the north
coast of Cuba in 36° N., the true latitudes being respectively 10°, 16°, 24°
and 23° N. On the chart of Bartolomeo Columbus, published by Wieser,
the errors are even more considerable.

• 'Zeitschr. f. Erdkunde,' IV., 1869, p. 403.

3 ' Raccolta Colombiana,' P. L, T. III. Serie B, No. 363. Simon de
la Rosa y Lopez, 'Catalogo,' p. xxxiii., believes that this note is by
Bartholomew Columbus.

* Dr. Scheppig suggests to me that there ought to be a full stop after
March 11, and that this was the date on which Jose made his report.

In another marginal noter' Columbus states that
he himself during various voyages to Guinea had
taken altitudes of the sun with the quadrant and other
instruments, and that his results agreed with those of
Master Yosepius and of others whom the king had sent
out. Columbus, in comparing the distances obtained by
dead reckoning with those corrected by observations for
latitude made by himself and others, concludes that El-
Ferghani was right when he gave the earth a circumference
of 20,400 miles, and reckoned 56f miles to a degree
of the Equator.

These marginal notes were evidently written long after
the events recorded, and Columbus may have made a
mistake in recording Jose's latitudes, just as he made a
mistake when he tells us in another marginal note that
the latitude of the Cape of Good Hope, as determined by
B. Dias, was 45° S.a Perhaps the 5 degrees refer to the
Castella S. Jorge da Mina, for the Ilhas dos Idolos (Los
islands) he in 9° 30' N. That Columbus himself should
have made such a mistake is not surprising, for he was a
very incompetent observer, but that Jose, a learned
astronomer, should have brought home so erroneous a
record is incredible. Still it is well known that latitudes
taken on board ship frequently differed to the extent of
several degrees from the truth, and on Soligo's Chart of
Portuguese Guinea, which I shall deal with fully in the
second part of this work, we read off the mouth of the
Niger " hie non apar polus," although that locality lies
more than six degrees to the north of the Equator.

Summing up, we find that the Junta, and more
especially its most active member, Jose Vizinho, advised
that vessels sailing beyond the Equator should observe
meridian altitudes of the sun for finding the latitude, that
experimental voyages were undertaken to test this
method, and Zacut's 1 Almanach perpetuum' was translated
and printed in order to facilitate the calculation of
the observations made. These reforms led naturally to
the adoption of graduated sailing charts, which had
previously been unknown in Portugal.

Behaim as an Astronomer.

In what way, it may be asked, could Martin Behaim
aid Dr. Rodrigo and Jose Vizinho in the task they had
undertaken ? He was no seaman, for at that time he had
crossed the sea but once, and that as a passenger, on a
voyage from Antwerp to Lisbon. He may have boasted
of being a pupil of Regiomontanus, and may have been
admitted, as a lad, to the observatory of that great
astronomer; but it is quite certain that he profited little
or nothing from lessons he may have received on these
occasions.7 In his letters, as far as they have reached us,

5 Imago mundi of Pierre d'Ailly ('Raccolta,' L. G, Serie C,
No. 490).

6 See my paper on ' the Voyages of Diogo Cao and Bartholomew
Dias' (' Geogr. Journal,' Dec. 1900).

' See p. 7.