112 
LONG 
GALLERY. 
Nat. Hist. 
different varieties of jasper, such as they are enume¬ 
rated by Werner, viz. the globular ox Egyptian jasper , 
found chiefly at Cairo in rounded pieces, which appear 
not to owe their form to rolling, but to be original, and 
produced by infiltration;—the riband jasper or striped 
jasper, the finest varieties of which are found in Si¬ 
beria ; — the variously-tinted common jasper ; — the 
agate-jasper, found only in agate-veins, and the porce¬ 
lain jasper, produced by the action of subterraneous 
fire on clay slate. The other half of this case contains 
opaline substances, viz., specimens, of the noble opal, 
which owes its beautiful play of colours to a multi¬ 
plicity of imperceptible fissures in its interior ;—the 
sun or jire opal; —the common opal, a translucent 
white variety of which, appearing yellow or red when 
held between the eye and the light, is called girasol; 
—the semi-opal, agreeing in its principal characters 
with the common;—specimens of a variety which, 
having the property of becoming transparent when 
immersed in water, is called hydrophane, and vulgarly, 
oculus mundi;— wood opal, or opalized wood ;—jasp- 
opal, referred by some authors to jasper ;—the menilite , 
called also liver opal, found at Menil-Montant, near 
Paris, in a bed of adhesive slate; a specimen of which 
is added. 
In the two next cases are placed the Silicates with 
one base. 
Case 25 contains the silicates of lime and those- of 
magnesia. To the former belongs the table spar or 
wollastonite from Mount Vesuvius, Nagyag, &c. ;■—to 
the latter, several of the minerals placed by . Werner 
into the talc genus:— steatite, the more remarkable va¬ 
rieties of which are, that of yellowish green colour 
from Greenland, and that from Gbpfersgriin in Ba- 
reuth, with small crystals of other mineral substances, 
especially quartz, converted into, and forming part of 
the massive steatite;—the kejfekil, or meerschaum, 
from Natolia, of which the well-known pipe-bowls are 
made, and that from Valecas in Spain ;—also a related 
substance, 
