Page 35 [35]
MINERALOGICAL REMARKS. 285
by the addition of a pure folution of vegetable alkali, yielded an
earthy precipitate ; this being wafhed and dried, gave fix grains of
aérated calcareous earth, and, being heated red hot, yielded three and ,
a half grains of quick lime.— From thefe experiments it appears,
that one hundred’ grains of the clear pebble have the following
component parts :
Siliceous Earth 74 7
Argil - 12
Lime - 7. \ grains weighed in:the red hot flate.
Magnefia 4 |
Iron - I
97
Lofs 3
100
rothly, The Mountain-Rock, which contains:the pebbles juft ex¬
amined, was analyfed in the fame manner, and gave the fame pro¬
du&s ; but with a-trifling difference in their proportions. Yet the
following remarkable. circumftance deferves to be noticed :—With
the blow-pipe it fwells up like alum or borax, with a crackling
noife and phofphorefcent light, into a remarkably porous, frothy,
very fragile fnow-white fubftance, which afterwards isinfufible. But
not lefs fingular is it, that the juft mentioned property of this
Mountain-Rock entirely ceafes, without lofing its remarkable ap¬
pearance, without a vifible alteration-of this appearance, and even
without a confiderable lofs of its weight, as foon as it is made red
hot
33