498 COSMOII. 



purarise. The strong oceanic current, which is directed 

 beyond the Pillars of Hercules from north-west to south-east, 

 might long have prevented the coast navigators from discover- 

 ing the islands most remote from the continent, and of which 

 only the smaller, Porto Santo, was found to be inhabited in 

 the fifteenth century ; and owing to the curvature of the earth 

 the summit of the great volcano of Teneriffe could not be 

 seen, even with a strong refraction, by Phoenician mariners 

 sailing along the coast; although I found, from my own 

 observations, that it was discernible from the slight elevations 

 that surround Cape Bojador,* especially in cases of eruption, 

 and by the reflection of a high cloud resting over the volcano. 

 It is even asserted that eruptions of Mount Etna have been 

 seen, in recent times, from Mount Taygetos in Greece.f 



In the enumeration of the elements of an extended know- 

 ledge of the universe, which were early brought to the Greeks 

 from other parts of the Mediterranean basin, we have hitherto 

 followed the Phoenicians and Carthaginians in their inter- 



the Phoenicians, Carthaginian*, Greeks, and Romans, perhaps even to 

 the Etruscans. 



* Compare the calculations in my Rel. Hist.,i. i. pp. 140 and 287. The 

 Peak of Teneriffe is distant 2 49' of an arc from the nearest point of the 

 African coast. In assuming a mean refraction of 0'08, the summit of 

 the Peak may be seen from a height of 1291 feet, and, therefore, from 

 the Montanas Negras, not far from Cape Bojador. tn this calculation, 

 the elevation of the Peak above the level of the sea has been taken at 

 12,175 feet; Captain Vidal has recently determined it trigonometrically 

 at 12,405, and Messrs. Coupvent and Dumoulin, barometrically, at 

 12,150. (D'Urville, Voyage au Pole Sud, Hist., t. i. 1842, pp. 

 31, 32.) But Lancerote, with a volcano, la Corona, 1918 feet in 

 height (Leop. v. Buch, Canarische Inseln, s. 104), and Fortaventura, 

 lie much nearer to the mainland than Teneriffe : the distance of the 

 first-named island being 1 15', and that of the second 1 2'. 



t Ross has only mentioned this assertion as a report (Hellenika, bd. i. 

 s. xi). May the observation not have rested on a mere deception? 

 If we take the elevation of Etna above the sea at 10,874 feet (lat. 

 37 45', long, from Paris 12 41% and that of the place of observation^ 

 on the Taygetos (Mount Elias), at 7904 feet (lat. 36 57', long, from 

 Paris 20 1'), and the distance between the two at 352 geographical 

 miles, we have for the point from which light was emitted above Etna, 

 and was visible on Taygetos, fully 48,675 feet, which is four and a half 

 times greater than the elevation of Etna. If, however, we might 

 assume, as my friend Professor Encke has remarked, the reflecting 

 surface to be 184 miles from Etna and 168 miles from Taygetos, its 

 height abr.vo the sea would only require to be 1829 feet. 



