370 DOMAIN XII. VOLCANIC. 



advancing to the meridian, unobscured by the 

 smallest cloud, and Reaumur's thermometer 

 stood in the tenth degree above the freezing 

 point. I was therefore in that temperature 

 which is most friendly to man ; and the refined 

 air I breathed, as if it had been entirely vital* 

 communicated a vigour and agility to my limbs, 

 and an activity and life to my ideas, which ap- 

 peared to be of a celestial nature." 

 Caverns. The currents of lava sometimes contain caverns 

 of a very considerable extent. In Iceland they 

 afford recesses for the flocks of sheep*. Dolo- 

 mieu has described a very remarkable one in an 

 island near Sicily; and he also found some in 

 the proximity of Etna, sometimes 30 feet in 

 height and 20 in breadth, the walls and vault 

 being as regular as if they were works of artf. 

 They are numerous ; and some, as he asserts, 

 many leagues in length. His explanation is, 

 that the surface of the lava forming a crust, is 

 sometimes arrested by impediments, while the 

 under current continues to flow ; so that upon 

 its complete elapse, the space remains void* 

 Thus bridges, of some miles of breadth or length, 

 are found on the Missouri, in North America : 

 - 



* Vor\ Troil Voy. d'Islande, Paris, 1781, the best edition revised 

 by the author, 

 t Lipari. Etna, 29 1. 



