COSMOS, VOL. II - World eBook Library

632 COSMOS
The influence exercised by Arabian civilisation through the
astronomical schools of Cordova, Seville, and Granada, on the
navigation of the Spaniards and Portuguese, cannot be overlooked.
The great instruments of the schools of Bagdad and
Charles V. (Arago, Annuairc du Bur. des Long., 1829, p. 152>) The
ancient Roman way-measurer (ratio a majoribus tradita, qua in via
rheda sedentes vel mari navigantes scire possumus quot millia numero
itineris feccrimus) is described in detail by Vitruvius (lib. x. cap. 14),
the credit of whose Augustan antiquity has, indeed, been recently much
shaken by C. Schultz and Osann. By means of three-toothed wheels
acting on each other, and by the falling of small round stones from a
wheel-case (loculamcntum), having only a single opening, the number of
revolutions of the outside wheels which dipped in the sea, and the number
of miles passed over in the day's voyage were given. Vitruvius
does not say whether these hodometers, which might afford "both use and
pleasure," were much used in the Mediterranean. In the biography of
the Emperor Pertinax, by Julius Capitolinus, mention is made of the
sale of the effects left by the Emperor Commodus, among which was a
travelling carriage, provided with a similar hoclometric apparatus, (cap.
8 in Hist. Aur/uxtce Script, ed. Lugd. Bat., 1671, t. i. p. 554.) The
wheels indicated both " the measure of the distance passed over, and the
duration of the journey, " in hours. A much more perfect way-measurer,
used both on the water and on land, has been described by Hero of
Alexandria, the pupil of Ctesibius, in his still inedited Greek manuscript
on the Dioptra. (See Venturi, Comment supra la Storia delV
Ottica, Bologna, 1814, t. i. pp. 134-139.) There is nothing to be found
on the subject we are considering, in the literature of the middle ages,
until we come to the period of several " books of Nautical Instruction,"
written or printed in quick succession by Antonio Pigafetta (Trattato di
Naviyazione, probably before 1530); Francisco Falero (1535 a brother
of the astronomer lluy Falero, who was to have accompanied Magellan
on his voyage round the world, and left behind him a " Rcgimiento para
observar la longitud en la mar"); Pedro de Medina of Seville (Arte de
Navegar, 1545); Martin Cortes of Bujalaroz (Breve Compendia de la
csfera, y de la arte de Naveyar, 1551); and Andres Garcia de Cespedes
(Reyimiento de Navigation y Hidroyrajla, 1606). From almost all
these works, some of which have become extremely rare, as well as from
the Suma de Geografta, which Martin Fernandez de Enciso had published
in 1519, we learn, most distinctly, that the "distance sailed
over" is learnt, in Spanish and Portuguese ships, not by any distinct
measurement, but only by estimation by the eye, according
to certain
established principles. Medina says (libro iii. cap. Hand 12), "in order
to know the course of the ship, as to the length of distance passed over,
the pilot must set down in his register how much distance the vessel
has made according to hours (i.e., guided by the hour-glass, ampolleta)
; and for this he must know that the most a ship advances in an
hour is four miles, and with feebler breezes, three, or only two." Ces-