104 NATURAL HISTORY. [^LONG 
ful specimens of wood converted into hornstone, being the 
wood-stone of Werner; hornstone balls from Hannstadt in 
Bavaria.—Of flinty a well known substance, some interest¬ 
ing varieties are deposited. The remainder of this and 
the whole of the following Case are occupied bj calcedonic 
substances. Among the specimens of common calcedon^^ 
the most remarkable are, the smalt-blue variety from Fel- 
sobanya in Transylvania, crystallized in obtuse rhombohe- 
drons; the branched and stalactical calcedony from Ice¬ 
land, &c.; the botryoidal, from Ferroe ; nodules, includ¬ 
ing water (enhydrites), from Monte Berico, near Vicenza, 
where they occur in volcanic rocks. 
Case 23. Calcedonic substances continued: cut and 
polished pieces of calcedony with red and black dendritic 
and other figures, called mocha stones; varieties with 
white, brown, and black, straight or curved lines, some 
of which were probably among the substances of which 
the costly vasa murrhma of the ancients were made ; 
red and yellowish varieties of calcedony called carnelian 
' — Plasma .— Heliotrope:, an intimate mixture of calce¬ 
dony and green earth, which, when containing disse¬ 
minated particles of red jasper, is commonly termed 
blood-stone.—The beautiful and much esteemed variety 
of calcedony called chrysoprase, hitherto only found at 
Kosemiitz in Silesia, and which owes its colour to 
oxide of nickel, as does the green siliceous earthy sub¬ 
stance, named pimelite, which accompanies it. To these 
are added specimens of some varieties of the siliceous com¬ 
pounds called agates, in which either common calcedony^ 
carnelian, or heliotrope generally form a predominant in¬ 
gredient. 
Case 24. One half of this Case is occupied by the dif¬ 
ferent varieties of jasper, such as they are enumerated by 
Werner, viz. the globular or 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 infil¬ 
tration ;—the riband jasper or striped jasper, the finest 
varieties of which are found in Siberia;—the variously- 
tinted common jasper ; —the agate-jasper, found only in 
agate veins, and the porcelain jasper, by the action 
of subterraneous fire on clay slate. The other half of this 
Case contains opaline substances (mostly hydrates of silica). 
