244 COSMOS. 



tion reminds one involuntarily of Hanno's journal of his 

 voyage, in which an island is referred to, enclosing a small 

 lake, from the centre of which a second island rises. The 

 phenomenon is said to occur twice, once in the Gulf of the 

 Western Horn, and again in the Bay of the Gorilla Apes, on 

 the West African coast. 14 Such particular descriptions may 

 be believed to rest upon actual observation of nature ! 



The smallest and greatest elevation of the points at which 

 the volcanic energy of the interior of the earth shows itself 

 permanently active at the surface, is a hypsometric considera- 

 tion possessing that interest for the physical description of 

 th earth which belongs to all facts relating to the reaction 

 of the fluid interior of the planet upon its surface. The 

 degree of the upheaving force 16 is certainly evidenced in the 

 height of volcanic conical mountains, but an opinion as to 

 the influence of comparative elevation upon the frequency 

 and violence of eruptions must be given with great caution. 

 Individual contrasts of the frequency and strength of similar 

 actions in very high or very low volcanoes, cannot be deci- 

 sive in this case, and our knowledge of the many hundred 

 active volcanoes, supposed to exist upon continents and 

 Islands, is still so exceedingly imperfect that the only deci- 

 sive method, that of average numbers, is as yet misapplied. 

 But such average numbers, even if they should furnish the 

 definite result at what elevation of the cones a quicker 

 return of the eruptions is manifested, would still leave room 

 for the doubt that the incalculable contingencies occurring 



the double encircling of a crater in the crater-lake, mentioned alike accu- 

 rately and circumstantially by Delamare, in his letter to Arago (Novem- 

 ber, 1842, Comptes rcndus de I'Acad. des Sciences, t. xvi, p. 756) is not 

 referred to. The great eruption in December, 1754 (a previous and 

 more violent one took place on the 24th September, 1716), destroyed 

 the old village of Taal, situated on the south-western bank of the lake, 

 which was subsequently rebuilt at a, greater distance from the volcano. 

 The small island of the lake upon which the volcano rises is called Isla 

 del Volcan. (Buzeta loc. cit.) The absolute elevation of the volcano of 

 Taal is scarcely 895 feet. It is, therefore, like Cosima, one of the lowest. 

 At the time of the American expedition of Captain Wilkes (1842) it 

 was in full activity. See United States Exploring Expedition, vol. v. 

 P . 317. 



14 Humboldt, Examen Critique de I' Hist, de la Geogr. t. iii, p. 135; 

 ffannonis Periplus, in Hudson's Geogr. Greed min. t. i, p. 46. 



15 Cosmos, vol. i, p. 227. 



