212 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [DcC. 13, 



to favour the hypothesis. But whether produced in the same man- 

 ner as the so-called volcanic or plutonic grits of other regions, by 

 contemporaneous segregation of the igneously-formed particles in the 

 bottom of a turbid sea, or by subsequent partial alteration of the 

 strata through the action of heat and gases, or by transport from 

 other rocks, it is clear that these small developments of granitic matter 

 are contemporaneous with the flysch. 



Now, it happens that in the same valley of Habkheren several large 

 granitic blocks also exist, which lying upon the surface of the an- 

 cient alluvium, or having been washed into water-courses, have at a 

 distance all the aspect of the usual Alpine erratic blocks, about the 

 transport of which there has been so much discussion*. The largest 

 of these lies on the surface of a boggy meadow, under which is a 

 great thickness of the coarse ancient alluvia on the east side of 

 the rivulet of Habkheren, as explained in the woodcut (fig. 21). This 



Habkheren. 



X, Erratic blocks. 

 7/. Ancient alluvium. 



g. Eocene flysch. 



block, so superposed to the ancient alluvia, is about 105 feet long by 

 90 feet broad and 45 feet high (above the marshy meadow), and 

 has therefore a mass of not less than 400,000 cubic feet. As it 

 consists of a peculiar granite f, now unknown to mineralogists in any 

 part of the Alps, Professor Studer believes that, like the very small 

 geodes and courses alluded to, this block was also included in the 

 formation of the flysch, and that during the disintegration of that 

 rock on the vertical sides of the valley, it has rolled down into its 

 present position. 



Extending this view, M. Studer accounts in a similar manner for 

 what he calls the blocks of the Bolghen, i.e. that they were derived 

 from pre-existing rocks, and were originally encased in the flysch 

 during its formation. After examining both spots, I cannot adopt 

 this opinion, nor can I regard the great block of Habkheren in any 



* In this memoir I shall not enter upon the question of the Alpine erratics, it 

 being my intention, at a future day, to give my opinions concerning their transport 

 and their relation to former glaciers. 



t According to Studer, this granite is composed of bluish-white and pink fel- 

 spar, the latter possibly albite, with white quartz, occasionally weathering yellowish, 

 and dark bronze-coloured mica in small crystals. 



