180 NATURAL HISTORY. [NORTH 
Case 46 contains various specimens of stalactic lime¬ 
stone, some varieties of which (such as those here deposited 
from Egypt, Shir Amin in Persia, &c.) bear the name of 
alabaster in common with the finer varieties of gypsum, 
and have, by Werner and other mineralogists, been re¬ 
ferred to fibrous limestone; the most beautiful modifica¬ 
tions of which latter are those from Cumberland and Swe¬ 
den, with pearly lustre (which has obtained for the former 
the appellation of satin-spar), and that in coloured layers 
from Africa. Also some specimens of granular limestone 
(granular marble) are placed in this Case. 
Case 47 contains the remaining varieties of carbonate 
of lime, among which may be specified the well-known 
depositions from the hot springs of Carlsbad in Bohemia, 
particularly the pisiform limestone, or p>ea stone, as also 
the globular variety (considered by some as magnesian 
limestone) found in the bed of a small river near Tivoli, 
and known by the name of Confetti di Tivoli,—the tufa- 
ceous limestone, in porous, spongy, cellular, tubular and 
other imitative forms, as incrustation on various objects, 
such as on the human skull here deposited, which was 
found in the Tiber at Rome; calcareous deposition formed 
in a square pipe in a coal mine in Somersetshire ; casts 
made at the baths of San Felippe, where moulds of 
medals, gems, &c., are placed in suitable situations to 
receive the spray impregnated with calcareous particles.— 
Chalk.—Anthraconite or madreporite .— Marie, &c. 
Case 48. In this Case, besides some specimens of 
carbonate of magnesia , or magnesite, from Baudissero 
and from New Jersey, are placed those substances which, 
being chiefly composed of carbonate of lime and car¬ 
bonate of magnesia, are called magnesian limestone, or 
dolomite, comprising Werner's rhomb-spar, dolomite and 
brown spar. Among the varieties of the first of these 
subspecies are those called mi emit e, tharandite, and some 
modifications of pearl spar; among those of dolomite, 
a remarkable one is that from Pittsfield, Massachusetts, 
North America, which exhibits a considerable degree of 
flexibility: and another having the same property will be 
found among the singular varieties of magnesian limestone 
from the vicinity of Sunderland. 
