116 
NATURAL HISTORY. 
[long 
depositions from the hot springs of Carlsbad in Bohemia, 
particularly the pisiform limestone, or pea 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 - 
eeous 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.—Anlhraconite or madreporite .— Marie , &c. 
Case 49. 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 flrst of these 
subspecies are those called miemite, tliarandite , 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. Of the varieties of 
Werner's brown spar or pearl spar, which in some cases 
is with difficulty distinguishable from rhomb spar, several 
interesting specimens for figure, colour and lustre, are de¬ 
posited in this Case, and continued in 
Case 50, which is partly occupied by those fibrous 
varieties of brown spar, several of which were formerly 
referred to common fibrous limestone.— Carbonate of iron, 
or sparry iron ore, crystallized, fibrous, massive, and bo- 
tryoidal (sphcerosiderite of Hausmann).— Carbonate of 
manganese, in globular and botryoidal shapes of various 
shades of rose colour, on sulphuret of manganese, &c. 
The remainder of this glass Case is occupied by the 
several varieties of carbonate of zinc, (also called calamine, 
in common with the silicate of zinc in Case 26) crystal- 
