25b COSMOS. 



and stars." It can not at present be decided whether, at tiiu 

 close of the fifteenth century, the use of the log was known as 

 a means of estimating the distance traversed while the direc- 

 tion is indicated by the compass ; but it is certain that Piga- 

 fetta, the companion of Magellan, speaks of the log {la catena. 

 a 2>oppa) as of a well-known means of measuring the course 

 passed over.* 



* In all the writings on the art of navigation which I have examined, 

 I have found the erroneous opinion that the log for the measurement ot 

 the distance traversed was not used before the end of" the sixteenth or 

 the beginning of the seventeenth century. In the EncyclopcBdia Bri- 

 tannica (seventh edition, 1842), vol. xiii., p. 416, it is further stated, 

 " The author of the device for measuring the ship's way is not known, 

 and no mention of it occurs till the year 1607, in an East Indian voyage 

 published by Purchas." This year is also named in all earlier and later 

 dictionaries as the extreme limit (Gehler, bd. vi., 1831, s. 450). Nav- 

 arrete alone, in the Dissertacion sobre los Progresos del Arte de Navegar, 

 1802, places the use of the log-line in English ships in the year 1577. 

 (Duflot de Mofras, Notice Bio graphique sur Mendoza et Navarrete, 1845, 

 p. 64.) Subsequently, in another place {Coleccion de los Viages de los 

 Espanoles, t. iv., 1837, p. 97), he asserts that, "in Magellan's time, the 

 speed of the ship was only estimated by the eye (a ojo), until, in the 

 sixteenth century, the corredera (the log) was devised." The meas- 

 urement of the distance sailed over by means of throwing the log, al- 

 though this means must, in itself, be termed imperfect, has become of 

 such great importance toward a knowledge of the velocity and direc- 

 tion of oceanic currents, that I have been led to make it an object of 

 careful investigation. I here give the principal results which are con- 

 tained in the sixth (still unpublished) volume of my Examen Critique 

 de V Histoirc de la Giographie et des Progres de V Astronomie Nautique. 

 The Romans, in the time of the republic, had in their ships way-meas- 

 urers, which consisted of wheels four feet high, provided with paddles 

 attached to the outside of the ship, exactly as in our ateam-boats, and as 

 in the apparatus for propelling vessels, which Blasco de Garay had pro- 

 posed, in 1543, at Barcelona to the Emperor Charles V. (Arago, An- 

 nuaire 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 de- 

 scribed in detail by Vitruvius (lib. x., cap. 14), the credit of whose Au- 

 gustan 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 fi'om a wheel-case (loculamen- 

 tum) having only a single opening, the number of revolutions of the 

 outside wheels which dipped in the sea, and the number of miles pass- 

 ed over in the day's voyage, were given. Vitruvius does not say 

 whether these hodometers, whicn might afRjrd " both use and pleas- 

 ure," 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 trav- 

 eling carriage provided with a similar hodometric apparatus (cap. 8 in 

 Hist. Augustce Script., ed. Lugd. Bat., 1671, t. i., p. 554). The wheels 

 indicated both " the measure of the distance passed over, and the dura 



