12 Mr. Winch on the Geology of the Banks of the Tweed. 



taining numerous basaltic boulders, water-worn, as usual. 

 This soil is red ; but colour does not always indicate the na- 

 ture of the rocks below, for a red soil also covers the por- 

 phyries and sienites of the north of England and the south of 

 Scotland. By a cut on the side of the road immediately be- 

 yond Coldstream Bridge, the incumbent mass of loose earth 

 is shown to be not less than fifty feet thick, at that spot, from 

 the top of the bank to the road, and for fifty feet more, to the 

 brink of the stream, no rock is seen to crop out from under 

 the debris ; and subsequent remarks led me to think that this 

 part of the country was generally clothed by a diluvial soil of 

 considerable thickness. To avoid repetition, it may not be 

 amiss to enumerate the rocks which are the subject of these 

 notes. Excluding basalt, they are all stratified, and, with few 

 exceptions, dip towards the southward of east, but at very 

 different angles, some beds rather exceeding than falling short 

 of 4>6. The suite comprises dolomite, indurated marl, and 

 limestone containing gypsum, red and variegated sandstone, 

 with nodules of red ochre, bituminous shales and sandstones, 

 \vith vegetable remains, encrinal limestone, also with vegetable 

 exuviae, shale, with bivalve shells, and numerous beds of coal ; 

 the whole series appearing to rest upon transition rocks, 

 which, to the north-west and south-west form the Lammer 

 Muir and Cheviot range of mountains. 



At the distance of sixteen miles, in a direct line from the 

 sea, and in the vicinity of Carham, a small burn enters the 

 Tweed on its south side, dividing Northumberland from Rox- 

 burghshire. Here a bed of close-grained iron-gray basalt 

 occupies the bed of the river for a considerable distance, and 

 near Carham Church rocks of pale-brown dolomite may be 

 seen on its banks. This limestone seems to be superior to 

 the basalt, and is heaped together in irregular masses, but that 

 these are a part of a regular stratum is evident, for at Had- 

 don Rigs, a mile south from this place, the stone is quarried 

 to the depth often feet for agricultural purposes, though, from 

 the veins of reddish-brown chert which pervade it, the produce 

 of pure lime is much diminished. Besides chert, calcareous 

 spar occurs in the rock, which, at the quarry just noticed, is 

 about ten feet thick, with a covering of ten feet of soil. The 

 next point where rocks are exposed to view is on the north 

 side of the river ; at the foot of Spring Hill, about a mile west 

 of Birgham. Here numerous thin strata of soft arenaceous 

 limestone, of an ash colour, interstratified with greenish-gray 

 indurated slaty marl, mixed with sand and mica, form cliffs 

 of nearly sixty feet high, and the river flows over strata of the 

 same description. Jn this limestone, veins of flesh-coloured 



compact 



