r 18- ] 
taneoufly, in a manner, upon the confolidation of the 
whole mafs of matter, in which they lie, and with which 
they conftantly bear the greateft analogy, as I have be- 
fore obferved. It is further remarkable, that common 
cryftals are parafitical bodies; whereas bafaltine cryf- 
tallizations, notwithftanding the peculiarities of their fi- 
gures, rather feem to form integral parts of the mafTes 
to which they adhere ; and feem to acknowledge, with 
them, one common and fimultaneous origin; like the 
rhomboidal and other cryftallizations in granites, and 
other limilar vitrifiable compound hones. Nor does the 
common flow and limited principle of cryflallization 
feem at all adequate to fo great an effect, which feems ex- 
clufively attributable to an igneous fluid, on the general 
concretion of which, the organic principle may be fup- 
pofed to have operated fimultaneoufly in a large mafs, 
and produced thefe bodies in the fame manner as a lin- 
get of metal concretes at once in the mould. No other 
mode of generation feems reconcileable with the phae- 
nomena of bafaltine aggregates, as I fhall more fully 
prove in the account of thofe of Auvergne and Velay. 
Nor do I pretend to determine how ftridfly this fimulta- 
neous concretion of parts may be applied to the organi- 
zation of fuch bodies, having ufed that expreflion rather 
in oppofition to the flow and interrupted fuccellion, that, to 
all appearance, takes place in the formation of common 
cryfcals. It feems alfo further evident to me from the 
phsenomena, that prifmatic bafaltine cryftallizations, 
and other regularly figured vulcanic groups (for others 
have 
