128 Sir Charles Lyell [April 15, 



reposing on the face of the great precipice at the head of the Val del 

 Bove, under the sunk space called " The Cisterna." This remarkable 

 current has a mean inclination of 35°, and the central stony layer is 

 seven feet thick. Above and below are parallel overlying and 

 underlying masses of scoriae five and seven feet thick respectively. 

 The flanks of the stream have been undermined and denuded by that 

 constant waste which makes the innumerable dikes to stand out in 

 relief on all the precipices surrounding the Val del Bove. Perhaps, 

 also, in this instance, the lateral excavation of the lava may have been 

 assisted by a rush of water like that of 1755, commonly called 

 Recupero's flood, which descended the same precipice, the " Balzo di 

 Trifoglietto." Suggestions were then offered on the probable cause of 

 that singular inundation, which swept in a few hours from near the 

 summit of Etna through the Val del Bove to the sea. The Canon 

 Eecupero traced its course, a few months after the event, by following 

 the line of sand and boulders which it had left in its track ; and calcu- 

 lated that the volume of water was so great, that, had all the snows of 

 the top of Etna been melted instantaneously, they could not have fur- 

 nished enough water for such a deluge. lie, therefore, concluded 

 that the water was vomited forth from the sunmiit-crater itself. Sir 

 C. Lyell conjectures that there may have been masses of ice in the 

 cone during the eruption which is recorded to have accompanied the 

 flood of 1755, and the ice may have been suddenly melted by hot 

 vapours and injected lava. In support of this hypothesis, he mentioned 

 his having ascertained the continued existence, in 1858, of thje same 

 glacier which was alluded to by him, in the first edition of his Prin- 

 ciples of Geology, as occurring at the base of the cone, and which had 

 been quarried before 1828. This mass of ice the Catanians again 

 quarried, four years ago, to a depth of four feet, without reaching the 

 bottom. It is covered by ten feet of volcanic sand, and this again by 

 lava. The tale of the mountaineers, who assured Recupero that the 

 water of the flood of 1755 was hot, may have been correct, if the origin 

 here assigned to it be true. 



Some account was next given of the lavas of 1852-53, which were 

 still hot, and emitting columns of vapour at the time of Sir C. Lyell's 

 last visit. They were more voluminous, perhaps, than any ever poured 

 forth from Etna in historical times, except those of 1669, which over- 

 flowed a great part of the ciy of Catania. The narrative of the people 

 of Zafarana, of the manner in which the frontal wall of lava, 30 feet 

 high, and inclined at an angle of 37°, had crept slowly over green pas- 

 tures and vineyards, and overwhelmed habitations in the suburbs of 

 that town, reminded Sir Charles of similar tales which he had listened 

 to seven weeks before in the Alpine valley of Zermatt, wliere the great 

 glacier had, in the preceding spring, been pushing onwards with irresistible 

 force, an equally steep mound of stony fragments, forming the frontal 

 moraine by which green meadows, gardens, and chalets had been over- 

 whelmed. A description was then given of the changes brought about 

 by the lavas of 1852-53 in the scenery of the Val del Bove, and in that 

 of the lower Valley of Calanna, in the interval since 1828, when the 



