1821.] Mr. Weaver on F/oelz Formations. 351 



three feet to six fathoms thick, extending through the whole 

 district, with occasional interruptions in spaces of 60 to 170 

 fathoms ; consisting of limestone intermixed with brown iron- 

 stone, sparry iron ore, and lamellar heavy spar, and containing 

 laro-e drusy cavities, in which the heavy spar sometimes appears 

 in magnificent tabular crystals, one foot square. The bed reposes 

 upon bituminous marl shale, and is commonly covered by a bed 

 composed of an intimate mixture of limestone and fine granular 

 sparry iron ore, with drusy cavities, containing crystallized arra- 

 gonite: But beneath the bituminous marl shale, sometimes 

 appears a second ironstone bed. 



An ironstone bed occurs also below bituminous marl shale in 

 the gryphite limestone, near Bennowitz, Kbnigsee, and Blanken- 

 burg. 



These ironstone beds are sometimes accompanied by more or 

 less considerable deposits of copper ores. 



The preceding abstract will convey to the reader a general idea 

 of the relations of the lower limestone formation of M. Freiesle- 

 ben; but to elucidate more fully the peculiarities displayed by 

 that formation in different tracts, the following remarks are 

 subjoined. 



In the Hartz, the copper shale is much richer in metal on the 

 southern than on the northern side of that country ; in the latter 

 quarter resembling rather a bad coal. In the forest of Thuringia 

 also it is metalliferous only in particular quarters ; while in others 

 it forms several beds, which, in some cases, exhibit a geological 

 affinity, as it were, to the beds of coal which lie not far 

 beneath it. 



On the western and north-western side of the Hartz, the zech- 

 stein forms, according to M. Haussmann, considerable ranges, 

 spreading far into Lower Saxony ; but at the south-western side 

 it is partly accompanied, and partly replaced by rauhkalk, which 

 there always occupies the place of rauhwacke ; and the same 

 rock is widely spread also over zechstein on the north-western 

 side of the Hartz. 



In Riegelsdorf, in Hesse, several thick beds of porous fetid 

 limestone alternate with equally thick beds of reddish and bluish 

 ciay (the latter sometimes containing gypsum), and with beds of 

 compact gypsum and swinestone ; the whole reposing on zech- 

 stein. 



On the north-western side of the forest of Thuringia, the 

 limestone formation reposes, partly on old red sandstone (rothe 

 todtliegende), partly on granite or other primary rocks. In the 

 former case, its stratification is pretty regular; in the latter, it 

 is irregular and interrupted, which is also the case on all the 

 other sides of the forest, the formation frequently appearing there 

 in detached and fractured portions. The upper beds have the 

 purer form of compact limestone; the lower consist rather of 



