21 
Saxony, derived from modifications of calcareous saloon. 
spar, also generally referred to conchoidal horn- Nat. Hjst. 
stone; also some beautiful specimens of wood 
converted into hornstone, being the woodstone 
of Werner. 
( Case In this case are deposited the dif- 
ferent varieties or subspecies of jasper, such as 
they are enumerated by Werner, viz. the Egyp- 
tian or globular jasper, found chiefly near Cairo 
in rounded pieces, which appear not to owe their 
form to rolling, but to be original and produced 
by infiltration ; the ribbon-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; the 
porcelain jasper, which is produced by the agency 
of subterraneous fire. — In this case are also con- 
tained the substances constituting the obsidian 
tribe, to which belong the pitch-stone, which is 
often confounded with semi-opal ; — the pearl- 
stone, so called from its colour and the small 
globular concretions of which it is composed ; 
— the obsidian, a remarkable variety of which is 
that found in globular pieces, at Ochotsk in Si- 
beria, near the small river Marekanka, from 
which it has obtained the name of Marekanite ; 
— pumice, which is not always of volcanic origin. 
Near these substances are placed some specimens 
of 
