388 STRUCTURE, AND MODE OF ACTION 



phenomenon which brings to light an otherwise unknown fish ? the 

 Pimelodes Cyclopum, called by the inhabitants of the highlands of 

 Quito " Prenadilla," and which I described soon after my return. 

 When, on the night of the 19th of June, 1698, the summit of a 

 mountain situated to the north of Chimborazo, the Carguairazo, 

 above 19,000 English feet high, fell in, the country for nearly thirty 

 English geographical square miles round was covered with mud and 

 fishes ; and seven years earlier a putrid fever, in the town of Ibarra, 

 was ascribed to a similar eruption of fish from the volcano of Im- 

 baburu. 



I recall these facts, because they throw some light on the differ- 

 ence between the eruption of dry ashes and miry inundations of 

 tufa and trass, carrying with them wood, charcoal, and shells. The 

 quantity of ashes emitted by Vesuvius in the recent eruption, like 

 everything connected with volcanos and other great natural phe- 

 nomena of a character to excite terror, has been exceedingly exag- 

 gerated in the public papers ; and two Neapolitan chemists, Vieenzo 

 Pepe and Giuseppe di Nobili, notwithstanding the statements of 

 Monticelli and Covelli to the contrary, even describe the ashes as 

 containing silver and gold. According to the results of my re- 

 searches and inquiries, the thickness of the bed of ashes formed by 

 the twelve days' shower was but little above three feet, towards 

 Bosche Tre Case, on the slope of the cone where rapilli were 

 mingled with them; and in the plain, from 15 to 19 inches at the 

 utmost. Such measurements ought not to be taken in places where 

 the ashes have been heaped up by the action of wind, like drifted 

 snow or sand, or have accumulated from being carried thither by 

 water. The times are passed for seeking only the marvellous in 

 volcanic phenomena, in the manner of the ancients, among whom 

 Ctesias made the ashes of Etna to be conveyed as far as the Indian 

 peninsula. There are in Mexico veins of gold and silver in trachytic 

 porphyry; but in the ashes of Vesuvius which I brought back 

 with me, and which an excellent chemist, Heinrich Rose, has ex- 

 amined at my request, no traces of either gold or silver have been 

 discovered. 



Although the above-mentioned results, which are quite in ac- 

 cordance with the exact observations of Monticelli, differ much from 



