366 DOMAIN xii. VOLCANIC. ' 



his travels among the Alps. The observations he 

 has made, appear to me to explain the cause of 

 these different accounts, relative to the effect of 

 the air. on the top of Etna. When the height 

 above the level of the sea was two thousand 

 four hundred and fifty poles, or nearly such, 

 which he found to be that of Mont Blanc, every 

 individual felt more or less inconvenience from 

 the rarefaction of the air, as happened to him- 

 self and nineteen persons who accompanied him, 

 when in August 178? he ascended that moun- 

 tain. But when the elevation was much less, as 

 for example, nineteen hundred poles, some of 

 these persons felt no difficulty, among whom 

 was this naturalist ; though he confesses that he 

 began to experience inconvenience as he ascend- 

 ed higher. We have not indeed any certain 

 observations relative to the exact height of Etna, 

 as is sufficiently proved by the different esti- 

 mates given by different naturalists. Signor 

 Dangios, however, astronomer at Malta, in the 

 year 178?> measured the height of this moun- 

 tain by a geometrical method, and the public 

 anxiously expects the results, which will satis j 

 factorily solve this important problem. In the 

 mean time, from comparing the measures hitherto 

 assigned, the elevation of Etna above the level 



