121 



Remarks on certain Traces of a Formation of Primary 

 Quartz Rock which appears to have at one time existed in 

 the South of Scotland. By Wm. Stevenson, Dunse. 



In the course of some investigations regarding the composition 

 of the Old Red Sandstone Conglomerate which crosses the 

 eastern part of the Lammermoor chain and extends along its 

 southern flanks, the writer was surprised to find a remarkable 

 change in the character of the pebbles of which the conglom- 

 erate consists, take place near its south-western limits, where 

 it is overlaid by the sandstones and clays of that formation. 

 In all the localities among the Lammermoors where the Old 

 Red Conglomerate is seen, it is found to consist entirely of 

 water-worn fragments of greywacke and felspar porphyry 

 derived from the neighbouring hills. Quartz pebbles are 

 rare, as might be anticipated, from the small proportion which 

 the quartz veins amongst these hills bear to the other 

 mineral masses. In the course of the Blackadder, however, 

 immediately above Greenlaw and along a line running in a 

 north-easterly direction by way of Kyle's Hill, Polwartli Mill 

 and Choicelee, the conglomerate contains a vei y large quantity 

 of white and brown quartz pebbles, all much rounded by 

 attrition. These have a peculiar aspect, differing both from 

 the white crystalline quartz so common in the mica slate for- 

 mation of the Grampians, and the granular quartz of Islay, 

 Braemar, &c. Their parent rock has evidently been a 

 primary sandstone, some of the beds of which were white 

 and others reddish brown ; and these strata have undergone 

 an amount of metamorphism equal to that which any of the 

 primary strata in the Highlands of Scotland have experienced. 

 For many miles to eastward of the above named localities 

 these pebbles are strewn over the surface in great numbers, 

 and enter largely into tlie composition of the superficial 

 gravelly deposits. This is especially the case along a line 

 extending E.N.E. from Choicelee, these scattered pebbles 

 having been mainly washed out of the conglomerate in the 

 neighbourhood of that locality. 



A consideration of these facts naturally led to the question, 

 where did these quartz pebbles originally come from ? A 

 careful examination of the Old Red Conglomerate of Lauder- 

 dale shewed it to be composed almost wholly of materials 

 derived from the adjoining greywacke. Scarcely a pebble of 

 quartz was to be found. A survey of the whole range of hills 

 to the eastward of Lauderdale, resulted only in the negative 



