1866] GUMBEL — ON LAURENTIAN ROCKS. 95 



in Bavaria another remarkable deposit of crystalline limestone, 

 included in the Hercynian primitive clay-slate series on the south 

 and south-east border of the Fichtelgebirge, in the vicinity of 

 Wunseidel. This clay-slate formation, as we have already shewn, 

 overlies the Hercynian gneiss and mica-slate series, and is 

 immediately beneath the primordial zone of the Lower Silurian 

 strata met with in the Fichtelgebirge. It would thus seem to 

 correspond with the Cambrian rocks of Wales, and with the 

 Huronian system of Canada, as Sir Roderick Murchison has 

 already suggested. This view is confirmed by Fritzsch's discovery 

 of traces of annelids in the grauwacke of Przibram, and by the 

 occurrence of crinoidal steins and foraminiferal forms, according to 

 Reuss, in the limestone of the primitive clay-slates of Paukratz, 

 near Reichenstein. Thus our Hercynian mica-slate, with certain 

 hornblendic strata and chloritic schists belonging to the same 

 horizon, would occupy a stratigraphical position similar to the 

 Labrador series, or Upper Laurentian, of Canada. 



The crystalline limestone of the Fichtelgebirge forms in the 

 primitive clay-slate two nearly parallel bands, which I conceive to 

 be the outcrops of one and the same stratum, on the opposite sides 

 of a trough. It presents several parallel beds separated by inter- 

 vening bods of the conformable clay-slate. 



The limestone strata near Wunseidel dip from 50° to 75° S.E., 

 and sometimes attain a thickness of 350 feet. They are in many 

 places dolomitic. * * * * Spathic iron, 



in nests and disseminated, characterizes this rock, and by its 

 decomposition gives rise to the valuable deposits of brown hematite, 

 which are worked along the outcrop of the limestone band. 

 Among the other minerals may be mentioned graphite, in crystal- 

 line plates, and also in small round grains and rounded compact 

 masses in the limestone ; besides which it frequently enters into 

 the composition of the adjacent clay-slate, giving rise to a 

 plumbaginous slate. Fluor-spar, chondrodite, tremolite, common 

 hornblende, serpentine, cubic and magnetic pyrites, are among the 

 minerals of the limestone. Quartz secretions are also met with, 

 but are evidently of secondary origin. The hornblende forms 

 rounded patches, remarkable twisted stripes, and banded parallel 

 layers, often of considerable dimensions, as in the specimens from 

 Wunseidel, which exhibit sheets of hornblende of from five to 

 fifteen millimeters, separated by limestone layers of from fifteen to 

 twenty millimeters in thickness. My examinations of the specimens 



