AND THE ADJOINING DISTRICT, BERWICKSHIRE. 43 
disturbed by their agency. Besides the veins and masses which are exposed, 
there are, undoubtedly, many veins and extravasated portions concealed among 
the strata. The principal masses of these traps which occur in the district are 
the following :— 
The Cumledge trap-dyke is a large body of trap of irregular thickness, which 
is seen in the bed of Oxendean Burn, near Cumledge House, and about 200 yards 
from the Whiteadder. It is here a sort of amygdaloidal greenstone, abounding 
in veins of zeolite, steatite, and other minerals, and is probably not more than ten 
yards in thickness. On-the west side it appears in contact with beds of a sort of 
cornstone, which are excessively hard and crystalline at the junction, while the 
trap becomes soft and earthy. On the east side a similar description of rock 
occurs. From this spot to the Whiteadder the strata are hid by debris, but ap- 
pear to belong to the coal measures, of which a fine section is presented a short 
way below the place where the burn joins the Whiteadder, in a cliff of more than 
eighty feet high. The shales, sandstones, and clays, are here seen dipping away 
from the dyke at angles, which increase in proportion to the proximity of the line 
of disturbance, until they become vertical, and even partially reversed. From 
this place to Preston Bridge, the strike of the strata is very regular, and parallel 
to the course of the dyke, which runs in a SSE. direction. At Preston Bridge its 
thickness is upwards of 100 yards. The strata of the coal-formation come close 
up to it on the east side; while on the west it cuts off the old red standstone. 
On the north bank of the river, about 300 yards above the bridge, it is seen in 
contact with strata of whitish sandstone and grey calcareous shales, which seem 
to be equivalents of those strata which elsewhere constitute the transition beds 
between the old red sandstone and coal measures. From this place it may be 
traced in the bed of the river, presenting, in general, the aspect of an amygdaloid, 
until we reach a place called “ Anglemyheart,”’ where it passes into a beautiful 
columnar basalt. The columns are irregular hexaedral prisms, not arranged ver- 
tically, but dipping at high angles to west. The basalt is more crystalline, and 
the columns more regular towards the interior of the mass. Towards the out- 
skirts it passes into an olive-coloured greenstone; and the latter graduates into a 
trap-tuff, composed of fragments of greenstone and metamorphic greywacke, 
agglomerated into a mass. 
This trap-dyke appears to run under the granite of the Staneshiel and Cock- 
burnlaw,—not, however, directly under the centre of the granitic mass of these hills, 
but more to the west side. In the glen or ravine between these two hills, and ex- 
actly in the line of continuation of the Cumledge dyke, a mass of basalt occurs, 
which has burst through the older rocks. There is every reason to believe that 
an eruption has taken place from a crater at this locality, and that the basalt now 
occupies what was formerly a volcanic vent. A considerable quantity of trap- 
tuff is seen in the bed of the river, in the vicinity of the basalt, and at intervals 
