160 GEOGNOSY AND GEOLOGY. 
cavities as asphaltum. It contains few fossils; the forms are principally 
molluscan. | 
These principal features of the upper division of the copper slate are 
generally accompanied by loam exhibiting concretionary masses~ and 
traversed by fibrous gypsum, spathic and brown iron-stone, gypsum and 
karstenite, and rock salt. The gypsum and karstenite are of great purity, and 
stand in such connexion as to permit the assumption that the one has arisen 
from the other. Their chemical composition teaches us that karstenite needs 
only to acquire a certain quantity of water to become gypsum. This 
explains the fact that pieces of karstenite are inclosed by a crust of gypsum, 
having absorbed enough water from the atmosphere for the purpose. In 
mining gypsum we frequently come to a nucleus of karstenite. A considerable 
increase of volume takes place in this combination with water, and thus 
by its irresistible expansive action shatters entire mountains. On this account 
gypseous masses, when of large extent, have a greatly riven aspect. The 
rough jagged surface is quite characteristic of gypsum, this being produced 
by the dissolving action of water (one part being soluble in four hundred 
of water) upon the softer parts of the rock.. The compact portions remain 
behind and cause the roughness. The fissures which arise by the increase 
in volume of the karstenite, collect large quantities of water, which also 
exerts its destructive influence on the inclosing rock. Cavernous excava- 
tions are thus gradually formed, which may increase so much in time as that 
the incumbent covering of gypsum, not finding sufficient support, may fall 
in, causing sink-holes, which are sometimes filled with a saline water. This 
upper group of the copper slate formation often contains powerful springs, 
and is extensively diffused in England, in the Hartz, in Thuringia and 
Saxony, in North America, and various other places. 
Among the geological equivalents may be enumerated the so called 
Frankenbergen formation, where limestone, slate clay, loam, sandstone, &c., 
rest on the transition slate and contain peculiar vegetable remains, presenting 
a distant resemblance to ears of grain, for which they were long mistaken. 
The copper sand ore formation of the west side of the Ural, constitutes 
another equivalent. 
Fossits or tHe Copper Stare Formation. The fossils of this 
formation are rare and not well known. The vegetable remains are 
composed of a few Fucoids, Lycopodiaceee, stems of not well determined 
monocotyledons and dicotyledons, Coniferee: Cupressites ulmanni (the 
Frankenbergen grain ears), &c.; the animals of a few corals, as E'scharites 
retiformis ; Radiata, as Hncrinites ramosus ; shells, as Productus aculeatus 
(pl. 38, fig. 1), Delthyris alata, and species of Mytilus. The Vertebrata 
consist of fishes and reptiles; trilobites are entirely wanting, and are 
apparently replaced by crustacea of a Limuliform character. Remains 
of fishes are numerous, and teeth of Acrodus larva (pl. 38, fig. 2), are 
characteristic of the zechstein. Reptiles first occur in the copper slate. 
The single genus known as belonging to this period, is found in the Mansfield 
copper slate, where its bones occur with fish remains. It is the Protero 
saurus, characterized by its long thin cylindrical teeth implanted in 
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