ixxxii NOTES. 



(Gehler, Bd. vi. 1831, S. 450.) It is only Navarrete, in the Disseitacion 

 sobre los progresos del Arte de Navegar, 1802, who places the use of the 

 xog-line in English ships in the year 1577. (Duflot de Mofras, Notice bio- 

 graphique sur Mendoza et Navarrete, 1845, p. 64.) Subsequently he affirms 

 in another place (Coleccion de los Viages de los Espafioles, T. iv. 1837, p. 97), 

 that " in Magellan's time the ship's speed was only estimated by the eye (a 

 ojo), until in the 16th century the corredera (the log) was devised." The 

 measurement of the distance sailed over by means of heaving the log, although 

 this means must in itself be tenned imperfect, has become of such great im- 

 portance towards a knowledge of the velocity and direction of oceanie 

 currents, that I have been led to make it an object of careful research. I 

 give here the principal results which are contained in the 6th and still unpub- 

 lished volume of my Examen critique de 1'histoire de la Geographic et des 

 progres de 1'Astronomie nautique. The Romans, in the time of the republic, 

 had in their ships apparatus for measuring the distance passed over, consist- 

 ing of wheels four feet high provided with paddles placed outside the ship, 

 just as in our steamboats, and as in the apparatus for propelling vessels which 

 Blasco de Garay had proposed in 1543 at Barcelona to the Emperor Charles V. 

 (Arago, Annuaire du Bureau des Longitudes, 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 fecerinius) is 

 described in detail by Vitruvius (lib. x. cap. 14), the credit of whose Augustan 

 age 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 siugle 

 hole, the number of revolutions of the outside wheels which dipped in the sea, 

 and the number of miles passed through in the day's course, were given. 

 Whether these hodometers were much used in the Mediterranean, " as they 

 might afford both use and pleasure," Vitruvius does not say. In the biogra- 

 phy of the Emperor Pertinax by Julius Capitolinus, mention is made of the 

 purchase of the effects left by the Emperor Commodus, among which was a 

 travelling carriage provided with a similar hodometric apparatus. (Cap. 8 in 

 Hist. Augustse Script, ed. Lugd. Bat. 1671, T. i. 554.) The wheels gave at 

 once " the measure of the distance passed over and the duration of the jour- 

 ney" iu hours. A much more perfect hodometer used both on the water and 

 on land has been described by Hero of Alexandria, the pupil of Ctesibius, in 

 his Greek still inedited manuscript on the Dioptra. (Sec Venturi, Comment. 

 opra la Storia delT Ottica, Bologna, 1814, T. i. p. 134139.) We liud 



