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 over- 

 looked. The great instruments of the schools of Bagdad and 



Charles Y. (Arago, Annuaire 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 fecerimus) 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 (loculamentum), having only a single opening, the number of 

 revolutions of the outside wheels which dipped in the sea, and the num- 

 ber 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 hodometric apparatus, (cap. 

 8 in Hist. Augmtce 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 manu- 

 script on the Dioptra. (See Venturi, Comment supra la Storia dell' 

 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 

 Navigazione, probably before 1530); Francisco Falero (1535 a brother 

 of the astronomer Ruy Falero, who was to have accompanied Magellan, 

 on his voyage round the world, and left behind him a " Regimiento para 

 observar la longitud en la mar"); Pedro de Medina of Seville (Arte de 

 Navegar, 1545); Martin Cortes of Bujalaroz (Breve Compendia de Id 

 esfera, y de la arte de Navegar, 1551) ; and Andres Garcia de Cespedes 

 (Regimiento de Navigacion y Hidrograjia, 1606). From almost all 

 these works, some of which have become extremely rare, as well as from 

 the Suma de Geografia, which Martin Fernandez de Enciso had pub- 

 lished 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, ampol- 

 leta) ; 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- 



