214 Mr Anderson on the Quartz District 



the mountains below Foyers, as we proceed eastward from the 

 margin of the lake. On the north side of Loch Ness, the 

 conglomerate is less abundant, but it is found on the summit 

 of the well known mountain named Mealfourvoney, which is 

 more than 3000 feet high. This is, therefore, one of the 

 greatest altitudes in Britain in which rocks of a conglomerate 

 character have been traced. The fragments which compose 

 this rock, may be described as different varieties of granite, 

 gneiss, mica-slate, quartz, and felspar ; chlorite may be also 

 occasionally detected. The fragments are angular and round- 

 ed, those of the latter form betraying undoubted marks of at- 

 trition. They also vary in magnitude, from the size of large 

 boulders to that of small grains. 



I shall now state the only distinctions which I have been 

 able to discover between the conglomerate rock which occurs 

 in the quartz district, and that which is associated with the 

 red sandstone. The former is much harder than the latter, 

 yielding to the blows of the hammer with far greater difficul- 

 tv. Again, in the conglomei'ate peculiar to the quartz-rock, 

 the fragments have often the appearance of imperfect crystals, 

 which have been separated and re-united. This character, 

 however, is not found in the variety of conglomerate which is 

 associated with the red sandstone. 



I may next observe, that the conglomerate which is found 

 on the summit of Mealfourvoney, contains a much smaller va- 

 riety of substances than is observed elsewhere, as they chiefly 

 consist either of quartz-rock itself, or of a variety of the same 

 which approaches to the character of gneiss. 



With regard to the structure of the quartz-rock, it is some- 

 times schistose, but in its general character can scarcely be 

 considered as stratified ; at least, it displays but imperfect- 

 ly any regular lamellar arrangement. The natural seams 

 and lines of fissility which its surface exhibits, are unlike 

 those of regular strata, having no uniform or parallel direc- 

 tion. There is also no regular dip or inclination to any par- 

 ticular point of the compass. 



This rock varies much in its liability to decomposition, but 

 in general it very strongly resists the action of the weather. 

 In decomposing, however, it is to be remarked, that the com- 



