Prof. Necker on the History and Progress of Geology. 297 
na, were far from presenting themselves in all their variety and 
generality. They had even appeared so local and accidental to 
Werner, that he did not deign to take notice of the mineralogi- 
cal distinction of their productions, and considered the decom- 
position of pyrites, and the inflammation of some beds of coal, 
as agents perfectly sufficient for producing subterraneous fires. 
Already, however, Auvergne and the Vivarais had drawn 
D’Aubuisson from the ideas which he had carried with him from 
Freyberg, and which he had laboured to support ; but it was 
from the great and beautiful observations of Humboldt in the 
Andes, of Von Bucli in the Canary Isles, of Beudant in Hun- 
gary, that there resulted the just appreciation of the nature of 
volcanic phenomena. 
I cannot here enter into details. Let it therefore suffice to say, 
that, from the small volcano of Stromboli, which has from time 
immemorial ejected stones and lava every quarter of an hour, 
to the immense Antisana, whose lateral eruptions only take place 
from one century to another, — from the still burning, to the ex- 
tinct volcanoes, — there is presented great variety in their nature 
and productions ; that, from some of these volcanoes, there issue, 
periodically, rivers of lava, whether from the crater, situated at 
the summit of volcanic cones, or from mouths formed upon their 
sides ; while others have no crater ; and the mineral torrents, is- 
suing from their base, present no appearance of an orifice toward 
their source. Lastly, the Canary Islands, and the remarkable 
volcano of Jorullo, have presented not only lavas, which, in flow- 
ing at the surface of the soil, have followed the declivities ; but 
masses, raised from the interior of the earth, in a state of incan- 
descence, which have replaced, with arid and desolate rocks, a 
vast extent of cultivated and fertile land. 
The variety of formations, in which we find craters of erup- 
tion, or craters of elevation, open, have demonstrated, that the 
fires, from which these different productions issue, can only be 
looked for beneath all the strata known, even the most ancient ; 
while the diversity of matters, which cover the one or other of 
these productions, testifies, that the phenomena, to which they 
owe their existence, are manifested at different periods, during 
the formation of the secondary deposits. There, then, we have 
the domain of fire considerably extended, in space and in time ; 
