232 STRUCTURE AND MODE OF ACTION 



terror, has been exceedingly exaggerated in the public papers ; 

 and two Neapolitan chemists, Yicenzo 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 researches 

 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 examined at my re- 

 quest, no traces of either gold or silver have been discovered. 

 Although the above mentioned results, which are quite in 

 accordance with the exact observations of Monticelli, differ 

 much from the accounts which have been current during the 

 short interval which has elapsed, it is nevertheless true that 

 the eruption of ashes from Vesuvius from the 24th to the 

 28th of last October (1822) is the most memorable of any 

 of which we possess an authentic account, since that which 

 occasioned the death of the elder Pliny. The quantity of 



