[ II ] 
by M. DESMARESTS, near le Mont M. sage alfo 
mentions another near St. Alcon, in the fame iirovincc. 
The Monte Roflb group is, however, not only curious in 
itfelf, but very interefling, on account of the great light 
it feems to throw upon the origin of granites in general, 
as I fliall have occafion to obferve more particularly here- 
after. It is remarkable that the columns, in the two dif- 
ferent groups of Monte Rolfo and San Giovanni, preferve 
refpe6lively the fame poiition, nearly parallel one with 
the other ; which is not commonly the cafe in other bafal- 
tine groups. For though the principal aggregate, which 
forms the Giants Caufeway, ftands in a direcftion perpen- 
dicular to the horizon ; yet other fmall detached groups 
of columns alfo appear in the hill above, that affe6f, by 
their pofition, different degrees of obliquity. Among the 
numerous bafaltine hills of Auvergne and Velay, in 
France, many of which I have lately vilited, and which 
feem to abound in thofe provinces more than in any 
other part of Europe, and perhaps of the known globe, 
nothing is more common, than to fee the columns of the 
fame group lying in all poffible dire6tions, as irregularly 
almoft, as the prifms in a mafs of common cryftal. Nor 
is this variety of pofition fo obfervable in fingie columns, 
as in whole mafles, or ranges of them, which often pre- 
fent themfelves, in the fame hill, difpofed in different 
Jirata^ or Rages, as it were, one above the other, many of 
which aff«6t very different, and even oppofite, dire(5tions. 
(d) De Rome Delifle EfTai de Criftallographie, Paris, 8vo, 1772. 
C z Thus, 
