Formation of Crystals ur Geodes. 
This was true not only of the spongy matter, but of the 
separate crystals, which we are entitled to consider as 
crystals of quartz, almost instantaneously deposited, from 
a rich siliceous solution. These crystals were of a rather 
dull white, without much lustre or transparency. | Their 
diameter was that of fine sewing silk, and their length not 
exceeding one sixth of an inch, It is much to be regret- 
ted, that no opportunity was afforded, of examining this 
fluid, so that it is impossible to say, whether it were some 
modification of water, or a distinct fluid. ‘The earthy de- 
posit ana the crystals were tasteless, and proved to be 
very sharp grit between the teeth. Mr. N. was so fortu- 
nate as to break another pebble, whose diameter was five 
ches by three,and consisting ¢ ofa mixture of hornstone and, 
cedon in whose centre 
inghe This. cavity, although strictly speaking not 
by a fluid, was nearly filled with the spongy sili- 
‘ceous deposite already described, but it was still moist, to 
such e as to form PRR or pons i mass, very 
soft and impressible ; this nao thee oon dried 
the intense heat of the so As there 
evaporate, so, as might have been expected,t 
few crystals pened still, they shot, “here and there, 
as in the other cavity. The spongy mass in the 
cavity of the abs stone admits a knife to penetrate 
it more than an inch, and portions of its surface have 
a mammillary and stalactical appearance. It is silex. like: 
the other. Many pebbles, from the same heap of ball: 
stones, have been brok o 
more of the fluid 
s 
e, however, been observed, some 
with the spongy siliceous deposite already mentioned, 1n- 
termixed with minute prismatic crystals, which last have 
however rather more lustre than those which were so rap- 
idly formed; and it is observable that the stone, forming 
_ mnost of the immediate walls of the interior of the cavities, 
s opaque enamel white, as if it had been penetrated 
id, and in some measure softened, by i inciple 
Other cavities were lin ni 
stals of transpar: 
well defined, but 
decentnn tin: 
4 : few cavities, the slic 
a ee 
ask is A 
i uk Cane ee ae OR CMM a eR Et he eee ea aa 
ern 
