AND THE ADJOINING DISTRICT, BERWICKSHIRE. 45 
which are likewise filled with trap. One of these already referred to, runs in a 
NNW. direction under the Knock hill, not however directly under tts centre, but to- 
wards the west side, and has thereby thrown the mass of felspathic rock, of which 
that hill consists, over to east, producing a partial retroflexion of the sandstone 
strata on that side. In this respect, it exactly resembles the Cumledge trap-dyke, 
which, as formerly mentioned, has thrown the granitic mass of the Staneshiel hill 
also over to eastward. Another striking point of resemblance between these two 
dykes, is the occurrence of an insulated mass of onion basalt, exactly in the line 
of continuation of each. The basalt in the line of the Borthwick trap-dyke oc- 
curs (in the channel of the burn which falls into the Whiteadder at Elm Cottage) 
about 3 miles NNW. from the Knock hill. It consists of concretionary masses of 
various sizes, up to a foot or more in diameter, composed of nuclei of bluish grey 
basalt, coarse in the grain, and very hard and heavy, surrounded by concentric 
coats of a tufaceous substance. There is a slip in connection with the line of fis- 
sure, from which the felspathic rocks of the Knock hill, and afterwards the augi- 
tic traps now under consideration, were erupted. This has caused a downcast of 
the old red sandstone strata on the west side to an extent of 300 or 400 feet. 
At Oxendean Commonhaugh, a mass of basalt is wrought in three quarries. It 
has been erupted through the old red sandstone, some of the strata of which are 
seen resting on its surface, much broken and altered by the heat. The original 
red of these beds has been changed to a dull purple, and the fragments into which 
they have been shivered are much indurated. The trap immediately subjacent is 
much debased by having absorbed, when in a molten state, a quantity of the de- 
tritus of the sandstone. The result is a curious compound, which is neither trap 
nor sandstone, but a mixture of both, and which graduates insensibly into the 
aqueous rock on the one hand, and the igneous on the other. In some places, 
also, the pulverized sandstone has got into fissures in the trap, where it has 
afterwards consolidated, presenting the singular phenomenon of veims of sandstone 
im basalt. The sandstone of these veins exhibits vertical lamination. 
The Basalt of Dunselaw is similar to the above, with which it is connected. It 
has also been erupted through the old red sandstones, which rise towards it 
all along the south side, as shewn by excavations in the town of Dunse and neigh- 
bourhood. A large block of metamorphic red sandstone, which is known by the 
name of the ‘* Covenanters’ Stone,” may be seen near the top of the hill. It seems 
to be a portion of a stratum which has been detached and borne up on the sur- 
face of the trap. It is hard and granular, and dips to ENE. at a high angle. 
The trap of the Castleknowes runs from Dunselaw in an ENE. direction, and 
probably joins the Cumledge trap-dyke at right angles. At the New Tile Works, 
about a mile east from Dunse, it is a beautiful amygdaloid, containing nodules 
of various minerals, coated with green earth. On the face of the bank south of 
VOL. XVI. PART I. M 
