Ioo 4n ANALYSIS of 
union with which they had loft their ftrong attraGion for 
water. 
Tue conftituent parts of thefe extrafts were next to be inve- 
ftigated. I foon perceived that they contained a portion of al- 
kaline falt not faturated with acid, which became evident when - 
a {mall quantity of them was wetted and applied to paper 
{tained with the juice of violets, or the colouring matter of the 
common purple radifh ; the colour in either cafe was changed 
toa green, I further collected and fcraped thefe extracts out 
of the glaffes, and placing each in a fmall filtre, 1 dropped di- 
{tilled water on them repeatedly, until the water came away 
from them infipid. The waters which had been thus filtrated 
through them were put into china cups, and the greater part 
evaporated with a gentle heat, the reft was allowed to evapo- 
rate fpontaneoufly ina dry room. Thus, a number of {mall 
faline cry{tals were formed, which were partly regular cryftals 
of common falt, and partly cryftals of an oblong and flatted 
form, larger than thofe of the common falt. Thefe larger 
cryftals were diftinguifhable, not only by their form, but by 
fome of their properties. They became white, opaque and 
mealy in dry afr, and being taken out, and tafted and tried in 
different ways, were found to contain fome of the foffil alkali 
in acryftalized ftate. 
Tue undiffolved matter which had remained on the filtrating 
paper, appeared by its properties to be totally or principally 
made up of filiceous earth. It was white and exceedingly 
fpungy and light. A fmall portion of it was triturated, and 
made into a pafte with water ; which pafte being laid on a piece 
of charcoal and dried, was heated intenfely with the blowpipe. 
No part of it was melted ; it was only contracted in its dimen- 
fions, and acquired a weak degree of cohefion. Another {mall 
portion was triturated dry, with an equal weight of aerated and 
exficcated foffil alkali ; and being put into a {mall platina fpoon, 
againft the bottom of which the flame of the blowpipe was 
; ftrongly 
