‘in his Paper on a saline Substance from Mount Vesuvius. 129 
The author appears not to be acquainted with such mountains . 
formed of primitive strata as are those observed in the central 
ridge of the Alps, in which is found the rock crystal, of a 
quartzeous nature, and even the purest quartz ; a fact directly 
contrary to his assertion: but the circumstances attending that 
crystal, and the crystal itself, indicate so incontestably its agueous 
origin and that of the strata in which it is found, that I shall 
describe the most important of them. 
At the time when IJ first travelled in the Alps, which was in 1744, 
rock crystal was employed, by cutting it, for various ornaments 
in houses, as lustres, sconces, and frames of various sorts, as 
may be seen in some ancient palaces. 
Considering that the circumstances attending that crystal in 
the strata could lead to the natural history of the latter, and as 
living at Geneva near the Alps, my brother and myself resolved 
to visit the places whence that crystal came, and to converse 
with those on the spot whose profession it was to extract it, in 
order to be informed of the nature of their work. 
After having travelled in many parts of the Alps, we generally 
found that rock crystal belonged to a’certain class of micaceous 
schistose strata, with many circumstances attesting the aqueous 
origin of that crystal, and consequently of the strata themselves. 
The following was the information which we received. 
A general fact is, that rock crystal is never found buéin ecvi- 
ties, the sides of which all around are covered with its prisms. 
Those of the inhabitants of the Alps who made that crystal the 
object of their pursuits, commonly called crystal-hunters, know- 
ing by the aspect of the sfrata those in’ which such cavities 
were likely to be found, and that they could not be discovered but 
in abrupt sides of the rocks, because the rubbish and grass cover 
the other parts, used a very hazardous method to find out those 
cavities. On the top of such abrupt sides in which they disvo- 
vered their characters, they bored some holes in the solid rock at 
different places, for the following purpose. They fixed very 
solidly poles in these holes, and twisted round them a ‘rope, at 
the one end of which hung a sort of basket: in this the most 
courageous of them was let down, allowing him a greater share 
of the adventure ; while his associates, to whom he trusted his 
life, held the other end of the rope at the top. . 
- As that man went down aloug the different parts of the rock, 
he struck it with a hammer, and by the different sound of the 
strokes he judged whether the rock was hollow, If there was 
no sensible difference in the sound, he did not think it worth 
while to open the cavily; but if the sound gave him the hope of 
finding a large cavity, then care was taken to secure him better, 
as he was to open it, and, entering it, to detach the prisms. 
Vol, 43, No, 190, Feb. 1814, I Fragments 
