258 



Islands *. I shall only mention some circum- 

 stances respecting the height, to which very con- 

 siderable fragments of rocks were projected by 

 the m6uths of the Chahorra. Mr. Cologan \ 

 reckoned from twelve to fifteen seconds during 

 the fall of these stones, that is to say, beginning to 

 count from the moment they had reached the 

 maximum of their height. This curious experi- 

 ment proves, that the mouth projected rocks 

 upwards of three thousand feet. 



The whole of the eruptions recorded in this 

 chronological statement belong solely to the 

 three islands of Pal ma, Teneriffe, and Lanze- 



* Bory de St. Vincent, p. 296. 

 f " Three of these stones," says Mr. Bory de St. Vincent^ 

 ** took from twelve to fifteen seeonds to rise till they were 

 out of sight and fall back to the ground." If such was the 

 observation of Mr. Cologan, the result of the calculation 

 would differ from that I have given ; but the observer expressly 

 says, in the manuscript in my possession .* *' De noche se 

 observocoa relox en mano y a muy corta distancia de la 

 tercera bocca del volcan de Chahorra, el tiempo que desde su 

 mas alto punto de elevacion hasta perderlas de vista en su 

 caida, gastaban las piedras mas faciles de distinguir y de tres 

 conque se hizo la experiencia, dos cayeron en cliez segundas 

 cada uha y la otra en quinze." Mr. Cologan observes, that 

 the duration of the fall was even something more than 

 fifteen seconds, because he could not keep th© stones in sight 

 till they touched the ground. .This kind of observation is 

 susceptible of great precision, as I was convinced from 

 similar experiments, which I made during the eruption of 

 Vesuvius in 1805. 



