Seite 35 [35]
OCR
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 examined, was analyfed in the fame manner, and gave the fame produ&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 appearance, 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
