42 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [DeC. 5, 



Croglin, and Newhiggin to Castle Carrock. The range of the Drift 

 thus pointed out may be regarded as closely approximating its upper 

 limit ; but on the brow of the mountain, in the neighbourhood of 

 Castle Carrock, the Drift-margin is a little above this place. 



From the neighbourhood of Castle Carrock, across the north end of 

 the Pennine chain, the upper reach of the Drift corresponds pretty 

 closely with the several collieries on the north side of the Mnety- 

 fathom Dyke, but extends a little further to the south in the valleys 

 of the Tyne, the Allen, and the Devil's Water. On the Tyne valley 

 it is found to occur about half a mile below Slaggyford ; in the Alien, 

 some 2| miles above Allen Town ; and in that of the Devil's Water, a 

 little below Lillswood. On passing somewhat direct from Midge- 

 holme pit to Eose Hill, the Drift is seen to lie on the southern and 

 northern sides of the mountain nearly up to its summit. To the west 

 of a line between the last-mentioned places the drift-materials have 

 much of a water-worn character. Small oval-shaped hills made up 

 of these materials are very prevalent on this area, and more particu- 

 larly so near the river Irthing. From the same line eastward to the 

 Tyne the Drift occurs very abundantly. The tributaries on the west 

 side of the Tyne, between Hartley Burn colliery and Haltwhistle, cut 

 deep into it and expose some good sections. There is a very fine sec- 

 tion directly down from this colliery, on the south-east side of the 

 Blackburn, opposite Low Mill House. In the mass here presented are 

 granites, green slates, porphyry, basalt. Mountain-limestone, shale, 

 New Bed sandstone, and some pieces of quartz. All these various 

 rocks are confusedly mixed in a firm clay. The clay is of a 

 reddish-brown colour and rather sandy below ; but higher up it is 

 more of a greyish blue and somewhat finer in texture. The granite 

 occurs in small pieces, some of which are angular, and others rounded. 

 The green slates, porphyry, and basalt are generally much rounded, 

 and occur as pebbles and small boulders. There are some blocks of 

 considerable size interspersed. The green slates and porphyry are 

 very plentiful here. The blocks of Carboniferous Limestone are not 

 much rounded, but are striated. The shale occurs in small thin 

 pieces. Some of the fragments of New Bed sandstone are angular, 

 and others rather rounded. The clay appears to be more sandy as it 

 increases in redness. 



About halfway between the Tyne and the Allen, from an elevation 

 corresponding with the top of the Coal-formation, the Drift spreads 

 somewhat thinly down the side of the valley to the river. The drift- 

 stones can be seen on the road down Plainmellar Common. Near 

 Plainmellar are some granitic boulders, probably of the Criffle Fell 

 granite. At Allen Town, on the east side of the water, the drift 

 consists of a stiffish and rather blue clay, in some parts inchning to 

 red, interspersed with angular sandstone very abundantly, and some 

 Carboniferous Limestone, with a good deal of shale -fragments, also 

 green slates and porphyry, and some portions of New Bed sandstone. 

 This heterogeneous mass has a thickness of 80 feet, and is overlain 

 by sand and shingle, which probably averages 12 feet. A mile or 

 so further up the Allen, but on the west side of the water, is another 



