GEOtOGY OF THE CAMPSIE HILLS. 85 



in the above section at Murray's Hall, the 

 coal has not yet been found, and by the other 

 taken near to the village of Campsie, the trap does 

 not exist ; but this last-mentioned section was 

 taken in one of the vales, in which situations, the 

 trap sometimes disappears, and these disappear- 

 ances seem, in a great measure, to have been ef- 

 fected by the attrition of rock masses, set in mo- 

 tion by heavy and rapid currents of water. 



In all situations of this district, where the trap 

 has disappeared, the vegetable or surface soil rests 

 upon a strongly tenacious blue clay, much mixed 

 with water- worn stones, and this blue clay rests 

 upon sandstone. Among the water - worn stones 

 imbedded in the clay, I seldom found specimens 

 of the native rocks of the district ; those which I 

 examined, consisted mostly of rocks generally 

 deemed of the oldest formations, such as quartz, 

 porphyries, granites, &c. ; the native beds of 

 which, are far distant to the north and west of 

 that part of the country. 



I have here mentioned above, that the disap- 

 pearance of the trap in some of the glens and 

 narrow vales, seems to have been produced by the 

 effects of the attrition of heavy bodies set in mo- 

 tion by a great force of water in rapid movement. 

 But this hypothesis requires explanation, and an 

 exposition of the phenomena upon w^hich it rests. 

 These, I shall here endeavour to describe, as the/ 

 appeared in some parts of this district. 



eg 



