TRANiSACTIONS OP THE SECTIONS. 627 



district, but slopes gradually from the hills. Mr. Milne ob- 

 served that the conglomerate of the old red sandstone is com- 

 posed of fragments, varying in size from small gravel to boul- 

 ders of a foot or two in thickness ; they consist of the same 

 rocks of which the neighbouring hills are composed, being either 

 grauvvack^ or trap, though the grauwacke fragments greatly 

 predominate. All the fragments have been completely rounded, 

 as if they had been worn down by the action of water ; not that 

 they seem to have been transported from a great distance, for 

 the fragments are now generally either at the very base of the 

 parent rocks or are in the iiiimediate vicinity of them ; but that 

 they seem to have been acted on like shingle, or a bank of gra- 

 vel at the foot of a sea-cliff, the pebbles of which have been 

 worn and smoothed by the incessant motion of the waves. 



The fragments are agglutinated together by a cement of small 

 gravel or sand, hardened by oxide of iron, which gives a red 

 tinge to the mass ; and wherever the fragments are oblong or 

 flat, their flat sides are almost always parallel to the line of 

 stratification. 



That these conglomerate rocks were deposited on the grau- 

 wacke, and from the debris which must have been collected at 

 the foot of them, is not only the only possible way of explaining 

 their present situation and appearance, but is proved by sections 

 at various points where the junction is seen. Mr. Milne then 

 referred to several drawings of these points of junction. 



The conglomerate is overlaid by a deposit of sandstone, which, 

 as already observed, is thinner near the edge of the deposit than 

 at greater distances from the hills. There is one character in 

 the mineralogical appearance of the rock, besides its red colour 

 and slaty structure, by which it is everywhere marked, viz. the 

 occurrence of white or greenish vphite spots or patches upon its 

 longitudinal fracture : these white spots do not generally exceed 

 two inches in diameter, being sometimes oval, but generally very 

 nearly circular. 



The upper part of the old red sandstone formation consists of 

 beds of red sand and red clay, which are so little consolidated, 

 that in the part of the country where they are best seen, (viz. be- 

 tween Whiteburn, Greenlaw, and East Gondon,) numbers of 

 hillocks and rounded knolls have been formed by the eff'ect of 

 the rains, and the rivulets which now encircle them. In many 

 places where the formation is less ferruginous, these upper beds 

 are worked for the sand they yield. 



No fossil remains of any kind have been found in this forma^ 

 tion. 



Since the deposition of these rocks they have been subjected 

 2 s 2 



