49 



volcanic objects: yet, in both tours, all these currents of 

 lava escaped him; which, by Mr. Demarest's account, 

 covered a district of country, eight or nine leagues in 

 diameter. 



. This negative evidence, against Mr. Desmarest's currents 

 of lava, is pretty strong: but Mr. Guetard is so good, as 

 also to furnish us with positive evidence, direct to the point; 

 for he assiu-es us, Volvic alone, of all the extinguished vol- 

 canos in Auvergne, produced lavas in any considerable 

 quantity; the others, to not more than the thickness of a 

 few inches; their ejections con&iMlBg merely of scoria, cin- 

 ders, pumices, and ashes. 



Mr. Guetard, also, gives (quite incidentally) a most im- 

 portant fact, decisive as to these currents of lava, to Avit, the 

 diameters of the craters;, the greatest of which measured but 

 from five to six toises (from 30 to 36 feet) ; yet, if we believe 

 what Mr. Desmarest calls currents of lava, to have been 

 actually such, we must allow^ that it was through these di- 

 minutive funnels such mighty torrents issued; and, in parti- 

 cular, the current, that formed the facade of Ladabraise, 

 one hundred feet high,. This I select, not as the greatest, 

 but because Mr. Desmarest sa3'^s, it issued at one jet.* 



In 



* Though Mr. Desmarest, who, on his mission, had visited the Italiah and Sici- 

 lian volcanos, often mentions the craters, from which his currents of lava issued, 

 he carefully suppresses their dimensions; the differeace between which, and 

 those of other volcanos, known to have produced' currejits of lava, must instantly 

 have struck every reader acquainted with such subjects. Sir William Hamilton 

 informs us, that the crater of JJtna W'as two miles and a half in circumference; 



that 



