Mr. Winch on the Geology of the Banks of the Tweed. 13 



compact gypsum* and nodules with crystals of brownish-red 

 selenite are tolerably abundant. The rocks lie very regular, 

 and dip, at a trifling angle, to the south-east. The relation 

 they bear to the red and variegated sandstones will be noticed 

 when the strata situated lower down the Tweed come under 

 consideration. 



In the bed of the rivulet called Firebourn, a slip or dyke is 

 worthy of notice ; in the language of miners, it casts up to 

 the east, and the thin strata of limestone and indurated marl, 

 before mentioned, may be seen in the water-course, dipping 

 at an angle of 40 in that direction. On the banks of the 

 river, at a trifling distance lower down, another slip divides 

 the rocks, and brings two beds of micaceous sandstone into 

 contact with the calcareous series ; the upper of these sand- 

 stone beds is slightly tinged red, owing to its mica being 

 oxidated, but the lower is of a pale yellowish-brown colour, 

 and ambiguous character, rather resembling a coal sandstone; 

 their aggregate thickness, with a thin micaceous parting, is 

 fourteen feet. Half a mile below Firebourn there is a ford 

 across the Tweed, noted in Border History ; its direction is 

 south-east, and may have been occasioned by the dyke. On 

 the south side of the river the ruins of Wark Castle stand on 

 an eminence sixty feet high, composed of calcareous strata, 

 similar in every respect to those at Spring Hill, but their dip 

 is in an opposite direction. These impure limestones seldom 

 exceed a foot in thickness, and gypsum is interspersed through 

 them. At about a hundred yards west of the Castle, rocks of 

 dolomite again crop out on the banks of the river, but to the 

 eastward this peculiar mineral was no more to be seen ; nor 

 could I thoroughly satisfy myself as to its geological position, 

 though I have every reason to believe that it rests upon the 

 basalt, and suspect this rock belongs to the same bed as oc- 

 cupies the north shore of the Tweed at Carham, and is here 

 again brought to the surface by the Firebourn Dyke. 



Again, passing to the north side of the Tweed, near the 

 Temple at the Lees, eight alternations of the same calcareous 

 beds as form the cliffs at Spring Hill and Wark, (except that 

 the lower stratum of limestone contains very minute bivalve 

 shells filled with calcareous spar,) occupy the bank and the 

 bottom of the river; their thickness above ground is about 

 ten feet, and their dip towards the north-west. No strata of 

 this description were again noticed for nearly six miles, and 



* Gypsum is also found at Fluers, some miles higher up the Tweed, on 

 its north bank, and has been found by the Rev. A. Baird, on the banks of 

 the Whiteadder, near Hutton Hall. Geological Essay on Berwickshire, 

 in the Preface of Johnston's Flora of Berwick, p. xxi. 



when 



