350 Mr. Weaver on Floetz Formations. [Nov. 



forest ofThuringia; while in the Hartz, it appears to be of rare 

 occurrence. 



According to M. Voigt, when the limestone mass becomes 

 less cavernous and more ferriferous, it appears as a yellowish- 

 brown, or brownish-grey, compact rock, firm and hard, or tender 

 and earthy. It occupies the place of rauhwacke and swinestone, 

 and it contains beds of swinestone, and sometimes also of bitu- 

 minous marl shale , and being distinguished by incidental strata 

 containing gryphites, M. A oigt has designated it by the name of 

 oryphite limestone,* On the other hand, M. Heim describes it, 

 when porous, as rauhwacke, differing only in respect of the man- 

 ganese and iron contained in it. That variety called zuchtwand, 

 a. calcareous ironstone, appears also to come under this head, 

 being near the surface yellow, in the interior brown, and at a 

 greater depth black, and passing in some parts into sparry iron 

 ore. It contains numberless nests and strings of calcareous spar, 

 and, in the vicinity of veins, also nests and strings of heavy spar. 

 And near Schmalkalden, it appears to contain also purer beds of 

 ironstone, constituting there the lower part of the formation, 

 from 17 to 30 fathoms thick, and reposing immediately on primary 

 rock. The calcareous ironstone is there connected with every 

 variety of brown ironstone, and, in the vicinity of veins, also with 

 occasional nests of sparry iron ore, and lamellar heavy spar. 



According to M. von Hoff, the ferriferous limestone, when 

 examined by the lens, is found to consist of small foliated grains 

 surrounded by an ochry earth, passing from yellow into dark- 

 brown. It is characterized by numerous veins of calcareous 

 spar, sparry iron ore, and manganese, which last substance 

 appears also in dendritic spots: At a greater depth, the colour 

 becomes darker, the predominance of iron greater, and at length 

 a subordinate bed of brown ironstone appears, consisting of every 

 variety of this substance, together with sparry iron ore, manga- 

 nese, and lamellar heavy spar, occasionally intermingled with 

 copper ores ; and thus constituted, the formation reposes on the 

 fundamental rock. Distinct deposits of copper ores, accompa- 

 nied with some manganese, appear also in the ferriferous lime- 

 stone, particularly when reposing on granite. 



In the vicinity of Gera, the beds of swinestone, black lime- 

 stone, and ferriferous limestone, which occur there, contain 

 gryphites, as well as those needle-like petrifactions, which were 

 considered as their spines even by Walch. The ferriferous lime- 

 stone contains also pectinites. 



The relations of the brown ironstone bed may be observed in a 

 distinct manner near Camsdorf, and in other parts of the Circle 

 of Neustadt. At the former place, it constitutes a bed, from 



* The following organic remains have been observed by Baron von Schlotheim in 

 gryphite limestone: gryphites aculeatus, g. cymbium, g. gigas, probably belonging to 

 gryphsea arcuata of Lamark, terebratulites alatus, t. lacunosus, pectinites textorius, 

 tellinites sanguinolarius. (See Petrefactenkunde.) 



