1816.] Royal Institute of France. 313 
classes; those in which sulphur acts a conspicuous part, and those 
in which muriatic acid predominates, He places Vesuvius among 
the latter. 
He points out, likewise, the constant smoke which rises from 
currents of Java, and which shows that it contains much moisture ; 
for these smokes are entirely aqueous. No flames appear; but the 
red-hot sand and stones, and the reverberation of the internal focus 
on the vapours which issue out, occasion the appearance of them. 
Lava flows slowly ; its ‘sides cooled down form a canal for it, and 
keep it elevated above the soil, all covered with scorie. We know; 
likewise, that its heat is not equal to that of melted glass; for when 
it incloses the trunks of trees, it does not char them to the centre. 
M. de la Groye, therefore, believes that the lava owes its fluidity to 
some principle consumed by the fusion, and that this is the cause of 
the difficulty of again fusing lava which has become solid.. The 
part of the mass which is not swelled into scoriz has an aspect 
quite stony. To it the Germans give the name of graustein. ‘The 
author compares the periods of the fusion of lavas to those through 
which those salts pass that melt after swelling up. He mentions 
curious facts respecting the prodigious duration of their heat; and 
concludes from them that they contain within themselves the prin- 
ciple of heating, and do not merely possess communicated heat. To 
all these remarks M. de la Groye addsa minute account of the great 
eruption of 1813, which produced an infinite quantity of lapillz 
and ashes, but the lavas of which did not reach the cultivated 
country. 
After having studied a burning volcano with so much care, M. 
de la Groye wished to ascertain the motives for arranging different 
mountains among extinct volcanoes. He accordingly visited one 
which M. de Saussure, and other great geologists, had placed in 
that class, but in which the obstinate Neptunists still found nume- 
_ Tous pretexts to support their doubts. 
This is the mountain Beaulieu, about three leagues from Aix, in 
Provence. ‘The inequalities of the surrounding country exhibit 
marks comparable to currents of lava. Its extent is about 1200 
fathoms in length, and 600 or 700 in breadth; its height about 
200 above the sea. It is surrounded to an indefinite distance by 
lime-stone. ‘Towards the east are the basaltic precipices which 
uppear to constitute the centre of the whole system ; but even in 
the basaltic part itself sea shells occur, and a great deal of lime- 
stone. The amygdaloids and basalts are covered with it in several 
parts. In others fragments of it are mixed, and constitute a kind 
of breccia. It has often penetrated the cavities of the amygdaloid. 
The principal rock is the floetz green-stone of the Germans, com- 
posed of felspar and augite, sometimes in such large grains that it 
resembles granite. Jt forms a long ridge,.and we pass from that 
rock by intermediate ones, comparable to trap properly so called, to 
common basalt containing frequently olivine, and of which Saussure 
observed some parts divided into prisms. There is, likewise, waeke, 
Vor. VII, N° 1V. x 
