i88 SCIENCE PROGRESS. 



erase, epidote, zoisite, augite (malacolite), hornblende, biot- 

 ite, anthophyllite, and cordierite. 



Farther south, on sheet 64 of the map, older rocks, in- 

 cluding phyllites, mica-schists and gneisses, come within the 

 influence of the syenite. The phenomena have been 

 briefly described by Dalmer (5). The phyllites are con- 

 verted into " Fruchtschiefer " like those known in the 

 Erzgebirge. The little concretionary patches consist of 

 a dark green substance containing a high percentage of 

 alumina and ferrous oxide and ten per cent, of water. 

 The chief effect of metamorphism in the mica-schists is 

 the production of andalusite, while the gneisses show no 

 appreciable change. 



The above areas lie to the west and north-west of 

 Dresden. The district to the south-east of that city, still 

 on the left bank of the Elbe, exhibits features of at least 

 equal interest, which have recently been described in several 

 memoirs by Beck (6). The chief intrusive masses with 

 which the metamorphism is connected are the Lausitz 

 granite and a syenite similar to those of Meissen and 

 Dresden. The rocks affected range from pre-Cambrian to 

 Devonian, and belong to very various petrographical types. 



The pre-Cambrian phyllites show the following suc- 

 cessive stages of alteration, as they approach the granite : 

 (i.) " Fruchtschiefer " with unaltered matrix, (ii.) "Frucht- 

 schiefer " with recrystallised matrix, (iii.) schistose micaceous 

 rocks, and (iv.) andalusite-mica rocks. The changes in- 

 volved are the gradual disappearance of the chlorite, with 

 concurrent development of brown mica and andalusite, the 

 recrystallisation of the quartz with increasing coarseness of 

 grain, and the production of what the author styles typical 

 "contact-structure," i.e., an interlocking of the irregularly 

 polygonal grains of such newly-formed minerals as quartz 

 and felspar. Precisely similar phenomena were previously 

 described bv Dalmer in the Western Erz^ebirore. Some 

 chlorite-gneisses associated with the phyllites are converted 

 into biotite-gneisses, while certain felspathic quartzites also 

 show a production of biotite and a recrystallisation of quartz 

 and felspar in a clear mosaic ("contact-structure"). 



