GALLERY.] 
NATURAL HISTORY. 
175 
tration ;—the riband-jasper or striped jasper, the finest 
varieties of which are found in Siberia;—the variously- 
tinted common jasper y—the agate-jasper, found only in 
agate veins, and the porcelain-jasper, p reduced by the action 
of subterraneous fire on clay-slate. The other half of this 
Case contains opaline substances (mostly hydrates of silica), 
viz., specimens of the noble opal, which owes its beautiful 
play of colours to a multiplicity 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 pro¬ 
perty of becoming transparent when immersed in water, is 
called hydrophane, or oculus mundi;— wood-opal , or opal- 
izedwood;— -jasp-opal, referred by some authors to jasper; 
—the menilile, liver or 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 the silicates of 
magnesia. To the former belongs the table spar or wollasto- 
nite from Mount Vesuvius, Nagyag, &c.;—the latter com¬ 
prehends several of the minerals placed by Werner in the 
talc genus:— steatite, the more remarkable varieties of 
which are, that of yellowish green colour from Greenland, 
and that from Gopfersgriin in Bareuth, with small crystals 
of other mineral substances, especially quartz, converted 
into, and forming part cf the massive steatite; variety 
called chalk of Brian^on;— keffekil, or meerschaum, from 
Natolia, of which the well-known pipe-bowls are made, and 
that from Valecas in Spain;—also a related substance, 
called keffekillite by Dr. Fischer, who discovered it in the 
Crimea;— lithornarge, the more remarkable varieties of 
which are, that of a reddish yellow colour in porphyry from 
Rochlitz, and the fine purplish blue variety from Planitz, 
formerly called terra miraculosa Saxonica, &c.— serpentine, 
the purer varieties of which (generally hydrates) are called 
noble serpentine: they constitute, in combination with pri¬ 
mitive limestone, the verde antico and some other fine green 
