1821.] . Mr. Weaver on Floetz Formations. 409 



conchoidal hornstone, and more rarely into sparry iron ore ; and 

 still more rarely they consist of brown iron ochre, which, falling 

 out, leaves the empty impression of the shell.* 



Coal. — Traces of coal appear only in the upper beds of the 

 shell limestone formation, but they are met with in many places; 

 generally consisting of a stratum of black clay, which includes 

 thin discontinuous layers, stripes, or laminae of slate coal ; the 

 mass being commonly much contaminated with iron pyrites, and 

 hence it soon disintegrates on exposure to the air, and forms 

 with water a viscid paste. From this circumstance, it has been 

 called clay-coal (letten-kohl) by M. Voigt. The bed, however, 

 is frequently composed for considerable distances of alum-shale 

 rather than coal, and, when burned, leaves a residuum of white 

 slaty clay. The coal is seldom fit for the forge, though a portion 

 of pitch coal has sometimes appeared in these beds, which have 

 been wrought in various quarters, at different periods, partly 

 with a view to coal, to vitriol, or to alum ; often, however, with- 

 out advantage. The clay, in which the coal lies, contains 

 remarkable impressions of plants, seed vessels, and seeds, which 

 are referred by B. von Schlotheim to unknown species of trees. 

 As an example of this kind of coal may be mentioned, the coal 

 near Kutzleben, in Thuringia, where one bed, 10-i inches thick, 

 composed of black clay, with single thin stripes of coal, and 

 covered with greenish-grey marl, reposes upon the shell lime- 

 stone ; beneath which, at the depth of 14 fathoms, is a second 

 coaly bed in the shell limestone, from 10 to 16 inches thick. 

 This contains smiths' coal, beside pitch coal two or three inches 

 thick. The carbonaceous layers have varied, in different quar- 

 ters, from 8 to 21 inches in thickness.^ 



In tracing the extent of the shell limestone, M. Freiesleben 

 follows that formation into Thuringia, the Hartz, Lower Saxony, 

 the forest of Thuringia, Franconia, Suabia, France, the heights 

 of Jura, the Alps, Dalmatia, &c. partly relying on the authorities 

 of MM. Heim, Voigt, Hausmann, Flurl, Sec. And as a corrobo- 

 ration of part of that view, the remarks of MM. Ebel and von 

 Raumer may also be noticed ; the former of whom observes that 

 beds of oolite are found throughout the Jura chains, the grains 

 of which vary from the size of lentils to that of peas, and even 

 larger ; + and the latter remarks, that the newest shell limestone 



• I have seen most of the analogues of the organic remains noticed above in the shell 

 limestone of Gloucestershire, beside others not included in that list; e.g. in the lias 

 limestone, pinnites, plagiostomites, crabs, prawns, shrimps, spines of balistse ; and in 

 the oolite, corallites, orthoceratites, plagiostomites, volutites, pinnites, arcacites, cucul- 

 Leites, astarte, mactra gibbosa. (Sowerby). Several of the remains occurring in the 

 beds of the Has and oolite series are to be found depicted and described in M. Sowerby's. 

 Mineral Conchology. 



i As an analogous formation in England, we may refer to the bad coal found in the 

 oolite of the eastern Moorlands of Yorkshire, in group No. 13 of Mr. Greenough's Geo- 

 logical Map ; and also to the bituminous slate clay, called Kiuuueridgc coal, in group 

 No. 10 of the same Map. 



t EbeL Alp«nbau, tol. ii. p. 109. 



