Dr. Borre's Mbtices of Foreign Geology. 189 



England is a deposit of this kind, alternating with the oldest 

 part of the 1st floetz liiTiestone of Werner.) The transition 

 class ends with the porphyries,or the secondary class commen- 

 ces with them. The porphyries and trap rocks (which Dr. 

 B. considers as local igneous formations) appear very dif- 

 ferently in many places. In Cumberland, and the Fichtels- 

 gebirge the grau wacke contains masses of porphyritic 

 and trap rocks, beds of reaggregated rocks of this class, 

 with here and there masses of Sienite or sometimes hillocks, 

 often containing hypersthene, or diallage. The superior 

 and inferior surfaces of these masses are often scorified — 

 some cavities appear to have been filled up by infiltration. 



In some countries the porphyries have broken out of the 

 primitive schistose rocks, and now form dykes with hillocks 

 of porphyries and of reaggregated porphyritic masses. In 

 some places, as the Erzgebirge, they are mere dykes, 

 as these were once taken for the beds of porphyry in the 

 gneiss, on the contrary gneiss contains no beds of porphyry, 

 and even the greatest part of the beds of granite in gneiss 

 are only veins, as for instance in Sweden and Finland. 



In the Erzgebirge, the dykes have much altered the gneiss, 

 and it appears to have been also affected by acid vapors. 

 Sometimes you see below the gneiss or transition clay slate 

 the porphyritic matter, having every appearance as if it had 

 been thrown up from below, and in some places you observe 

 crystals of pyroxene in the gneiss where it is in contact with 

 the dyke. 



The coal formation is found upon the old red sandstone 

 in Scotland, and Silesia ; at Thorandt near Dresden and at 

 Halle it is belozv, and in Bohemia it is in the old red sand- 

 stone. 



On the Rhine and in the northern parts of the Alps, the 

 Zechstein or 1st floetz limestone is imbedded in the coal- 

 field. I explain this in the following manner; the old red 

 sandstone is only a conglomerate of porphyritic matter, 

 when the porphyries have appeared sooner as a local deposit, 

 you find the coal field above the sandstone ; when they have 

 appeared during the deposition of coal, the coal field is cov- 

 ered by the sandstone, and when they have appeared 

 through the whole period, there you find hardly any of the 

 sandstone of the coal formation, but the coal field is in the 

 old red sandstone. On the other hand where no porphyries 



