Mr Scropc on Humboldt's Theory, 6fC. 55 



de las Cuevas to the Picacho del Mortero ; and it is thus also 

 that the bocche nove of Vesuvius are ranged along the pro- 

 longation of a chasm. Do not these analogies entitle us to 

 suppose that there exists, in this part of Mexico, at a great 

 depth in the interior of the earth, a chasm in a direction 

 from east to west, for a length of 137 leagues, along which 

 the volcanic fire, bursting through the interior crust of the 

 porphyritical rocks, has made its appearance at different 

 epochas from the gulf of Mexico to the South Sea? Does 

 this chasm extend to the small group of islands called by M. 

 Collnet the archipelago of Revillagigedo, around which, in 

 the same parallel with the Mexican volcanoes, pumice-stone 

 has been seen floating ? Those naturalists who make a dis- 

 tinction between the facts which are offered us by descrip- 

 tive geology and theoretical reveries on the primitive state of 

 our planet, will forgive us these general observations on the 

 general map of New Spain. Moreover, from the lake of 

 Cuiseo, which is impregnated with muriate of soda, and 

 which exhales sulphuretted hydrogen, as far as the cityofVal- 

 ladolid, for an extent of 48 square leagues, there are a great 

 quantity of hot wells, which generally contain only muriatic 

 acid, without any vestiges of terreous sulphates or metallic salts. 

 Such are the mineral waters of the Chucandiro, Cuinche, San 

 Sebastian, and San Juan Tararamco. 



Art. IX. — Observations on Humboldt's Theory of the Volca- 

 no of Jorvllo. By G. Poulett Scrope, Esq. Secretary 

 to the Geological Society. 



The theory of the volcano of Jorullo, given by Baron Hum- 

 boldt in the preceding article, has been very ably examined 

 by Mr Scrope in his Considerations on Volcanoes, a new and 

 interesting work which has just appeared. 



From a personal examination of almost all the extinct, as 

 well as the active volcanoes of Europe, Mr Scrope was led to 

 the opinion, that they display a remarkable uniformity of 

 character, presenting few other variations than what depend 

 on the degree of energy they have displayed. The phe- 

 nomena of Jorullo, however, as explained by Humboldt, 



