20 PROF. T. m'KENNT hughes on the POSITION" 



3. On the Position of the Obermittweida Conglomerate. By 

 Prof. T. M'Kennt Hughes, M.A., P.G.S. (Eead I^ovember 9, 



1887.) 



On the south-west side of the little valley of the Mittweida, within 

 an easy drive from Annaberg, about 25 miles south of Chemnitz, 

 and twice that distance south-west of Dresden, there is a remarkable 

 section which seems to show a strong conglomerate, crushed, it is 

 true, but otherwise not much altered, intercalated among the gneiss 

 and mica-schist which cover so large an area in that part of Saxony. 

 It is therefore of some importance to inquire how far it would be 

 possible to admit other explanations of the section than that which 

 seems at first sight to be the obvious inference, and to consider 

 whether an examination of the rocks in the field and a comparison 

 of the mode of occurrence of other similar conglomerates render 

 it possible to ex]7lain away the apparent interstratification of the 

 conglomerate and gneissic series. 



I am indebted to Professor Credner, not only for much information 

 on the subject, but for references to previous writers. The first 

 notice seems to be that of Dr. Saner, of Leipzig *, under whose 

 guidance I visited this locality a few years ago, and whom I take 

 this opportunity of thanking for much kind attention. 



The occurrence o£ this conglomerate is indicated on the Geological 

 Map of Saxony and in the section given in its margin f. 



Professor Justus Eoth, of Berlin, wrote a paper % upon these con- 

 glomerates in 1883, and afterwards referred to them in his work 

 on General and Chemical Geology §, published in Berlin in 1887. 



Yon Hauer referred to this rock as only something like a con- 

 glomerate. As Prof. Both did not allow that the gneisses were of 

 sedimentary origin, he, of course, could not admit that the so-called 

 pebbles Avere included rolled fragments, but referred them to con- 

 cretionarj^ action. 



Several geologists, Dr. Saner amongst them, have tried to get over 

 the difficulty by suggesting that the conglomerate was altogether 

 newer than the gneiss, and that it has been folded and faulted in. 

 So that my friend Professor Credner, not without justice, remarks 

 that we should not now put this explanation forward as a mere 

 hypothetical solution of a difficulty without off'ering some facts in 

 support of the view ; yet I venture, at my friend Professor Bonney's 

 request, to off'er my impression of the section. 



* " Ueber Conglomerate in der Glimmerschiefer-Formation des sachsischen 

 Erzgebirges/' Zeitschrift f. d. ges. Naturwiss. Band lii. 1879, p. 706. 



t Geolog. Speeial-Karte von Sachsen, Masstab 1-25000, Section Elterlein, 

 nebst zugehorigen Erlauterungen. 



\ Sitzungsbarichte der kgl. Preuss. Akad. der Wissenschaften zu BerHn, 1883 

 (PhysikaL-mathem. Classe) xxviii. 14 Mai. 



§ Algememe und Chem. Geologic, ii. Band, p. 428. Berlin, 1887. 



