284 DOMAIN XII. VOLCANIC. 



extinct volcanoes ; and that in Etna they 

 do not constitute the one thousandth part 

 of the whole; whereas, in Vivarois and 

 Auvergne, they form whole mountains. 

 Now most of these ancient volcanoes of the 

 Vivarois, appear to me, and many others, 

 to be mere creatures of imagination ; and 

 consequently, until the substances they 

 contain are proved to have been in fusion, 

 no definition, grounded on the appear- 

 ances of these substances, can pass for 

 that of real compact lava*. 



" In beds, however, of real undisputed 

 lava, some parts are found, that having 

 been pressed by the superincumbent weight, 

 are more compact than common porous 

 lava, and these, comparatively to the for- 

 mer, may be called compact ; but scarcely 

 more than a few square inches of their sub- 

 stance is destitute of visible pores. 



"Their colour is brown, yellowish, reddish 

 brown, bluish, or black, more rarely grey. 

 Their lustre 0,1. Transparency 0,1. 



* (See, on the contrary, the remarks of another Neptunist, Dau- 

 buisson, in Dom. I P.) 



