16 GEOLOGICAL MEMOIRS. 



in the Bergstrasse. A great many localities might be quoted for this 

 purpose, if one would take the trouble carefully to compare all the 

 local descriptions relating hereto. That, however, is little in accord- 

 ance with my design, for I well know that it is dangerous to endeavour 

 to explain in particular points of view the observations of another, 

 when the observer himself was not actuated by those views nor had 

 them in the least in his consideration. Having ojnfered these general 

 remarks, to which the concluding part of M. Scheerer's paper has 

 given rise, I will confine myself to the expressed wish of M. Delesse, 

 to notice briefly some few particulars, of my own observation, relating 

 to the occurrence of granular limestones in crystalline schists ; a phse- 

 nomenon also that is in part connected with that group of minerals, 

 which, it appears to me, generally where they occur to any extent, 

 originate in the contact of limestone with siliceous or clay-slates. 



Limestone of Tharand near Dresden. — Near Tharand the unfos- 

 siliferous clay-slate contains a fine-grained, grey, and somewhat dolo- 

 mitic limestone, in a layer-like mass sometimes of considerable thick- 

 ness. At the upper and lower surfaces of the limestone are very 

 numerous alternations of thin laminae of limestone and clay-slate. 

 The limestone is traversed by the great Tharand quartzose porphyry 

 vein, and along the line of junction of the vein and the limestone 

 there are sometimes peculiar drusy breccias, in which limestone frag- 

 ments are cemented together by calc-spar and brown-spar. Between 

 and in the fragments druses have been developed, so that sometimes 

 merely the walls of the druse cavity, only a line in thickness and form- 

 ing the outer surface of the fragment, is all that remains. In the 

 druses are found crystals of Brown-spar, Calc-spar, Heavy-spar, 

 Gypsum, Iron-pyrites, Copper-pyrites, Lead-glance, and Blende, but 

 none of those minerals that are so characteristic of the contact-sur- 

 faces of limestone and siliceous rock. A perfect melting and com- 

 mingling has not taken place at Tharand ; there is evidence only of 

 a low stage in the process of change. 



Limestone of Zaunhaus in Saxony. — This fine and highly crystallo- 

 granular limestone lies in the mica-schist of the Altenberg district, 

 and is parallel with its lamination. Above and below here also are 

 numerous alternations of limestone and mica-schist laminae. If we 

 fancy the Tharand limestone next to the enclosing clay-slate in a some- 

 what higher stage of change (but not absolutely melted), we have before 

 us the Zaunhaus conditions. The whole mass pf the Zaunhaus 

 marble, however, is moreover permeated by a large quantity of small 

 white mica-flakes parallel with the lamination. It is a Cipolino. 



Limestone of Wunsiedel in Bavaria. — This forms a thick and ex- 

 tensive bed in the mica-schist of the Fichtelgebirg, where, along a 

 long curved line between Trostau and Hohenberg, it has given rise to 

 a great number of quarries. It offers the appearance of a regularly 

 intercalated bed in the mica-schist, but it has lenticular thickenings, 

 and between these thicker portions it sometimes almost disappears. 

 At its surface this, like the very similar limestone of Arzberg-Redwitz, 

 is often accompanied with brown iron ore, which has apparently re- 

 sulted from the decomposition of spathose iron-stone. The limestone 



