Earths, argillaceous. 33. Casmemum. I2t 
’^^xacen. Cinereous, confining of diflinfl granulations. 
Pumex cinerarias. S\il. nat xii. 3 " 
Porus igneus. Wall, fy ft min, 2. ^.375. «. 1. 
Vo'can'C find. Ktrnuan miner. 1. #.410. 
Volcanic fands. fhomfon chcm. p 150. 
Found in the neighbouihood of VolcanoSj and are compofed of 
fmail hard grains varjdng in iize; they readily fink in watery 
and aie ufnallv mixed with fmail fragments of felfpar, lava, 
magnetic iron-llor.c, &c. they often cover a great extent of 
groutifi, fometimes to the extent of 50 leagues round the vol- 
cano, and levcral feet thick, 
» 
33. C/EMENTtJM. Confining of iron, alumina, 
a larger qiiantity of filica, and generally a fmail 
proportion of carbonate of lime : hardifh, light- 
ifh, porous, of an earthy texture, imbibing the 
water in which it is immerfed with a hilling 
noile, crackling wlien dried and prelled with the 
thumb, rough, without hiftre ; when powdered 
and beat up with water and quicklime becoming 
lb hard as not to be penetrated by water, eafily 
melting in the fire into a black fcoria. 
Colleaed into entire clifFs and vaft ftrata about volcanic 
mountain.', of a common form. 
Gioeai lilolov. I'ejaniian. p. 1 74. 
Tufss. Kirnoun mineral. ! . ^.414.’ 
Tutfvvacke. Schmeijfer mineral. 1. /. 187. 
Found in the neighbourhood of volcano', particularly in Italy, 
about Hapks and Rome, and confills of compaift maffes of 
pouzzolano, find, iUggs, pumice, and other ftones of v .1- 
canic origin : colour molUy fniake colour, cinereous, blacUlh, 
brown, ochraceous, yellowi(h-grcy, or brownilh yellow, 
rarely reddilh, greenilh or Variegated : it is commonly mag- 
netic, of an earthy frafture, and not cafily decompofed by the 
■aftion of the air ; fometimes it has a fmail mixture of bones, 
{hells and other calcareous fubllances, and then effervefees a 
little with acids. 
Eorniing large flratti under the furface of the common foil, 
of a common form. 
Camiencum ioduratum. Cronst, miner 207. n.^.z, 
Camiertu n indtiratura. Wall. fist, min, 1. ^• 97 ‘ 
Trafs or T'.rras. Kir-uean mineral l.p. 413. 
Trafs or Tarras. Zchmefter mineral, l. f, 187. 
VOL. vir. — CL 
