Notice of Active and Extinct Volcanos. 237 



Although the ingredients are too intimately mixed to allow 

 of our always ascertaining their nature by inspection — it can 

 always be done by the blow pipe — for trachyte melts into a 

 white enamel whatever may have been its color, while basalt 

 after fusion, retains always its original color. 



Felspathic lava is therefore, in the language of our author, 

 synonymous with trachyte, and augite lava with basaltic lava. 



The only essential ingredient of trachyte appears therefore 

 to be felspar while basalt always contains augite. 



1. Extinct Volcanos of France and Germany. 



Under this division of Professor Daubeny's work, we shall 

 not enter into much detail, because, should we be able on a 

 future occasion to give some account of the separate, work of 

 Mr. Scrope on the extinct volcanos of France and Germany 

 &c. we shall necessarily travel over the same ground and in 

 doing it we can if necessary revert to the present treatise. 



We believe much philosophical scepticism formerly existed 

 with respect to extinct volcanos. They were vaguely referred 

 to, but without decisive proof of their real volcanic origin, and 

 many persons very imperfectly qualified to judge of such ques- 

 tions, were sufficiently inclined to infer the existence of vol- 

 canos of former ages, wherever they saw a conical hill or al- 

 most any hill with a hollow on its summit, and porous stones 

 of whatever kind, were referred to a similar origin. It was a 

 very imposing and sublime idea, that volcanic fire, still active 

 in our planet, and still bursting forth in many places, with des- 

 tructive energy, had, in ages long past, erected agencies still 

 more extensive — covering provinces with ruins, and operating 

 even in the bed of the primeval oceans. The speculation 

 seemed however to claim quite as much affinity with poetical 

 as with philosophical conceptions, and it was not till the mid- 

 dle of the last century that the subject of extinct volcanos be- 

 gan to be investigated with accuracy and skill. 



The much disputed region of Auvergne, Velay and Vive- 

 rais, in France, has been often visited, and examined by able 

 geologists, and we believe that within a few years past, no one 

 of them has left that region, without being convinced that it is 

 of volcanic origin. The celebrated geologist D'Aubuisson 

 visited the country in question, with the strongest belief that 

 he should find this district of Neptunian origin, but he returned 

 a convert to the opposite opinion ; a change the more credit- 



