212 PROFESSOR FORBES ON THE GEOLOGY 
ous, which appear to be derived more immediately from boulders of that rock 
imbedded in the drift formation. It is also evident that the partial or complete 
removal of the barrier of altered rock just mentioned has changed the course of 
the Tweed, which appears once to have swept over the site of the present village 
and abbey of Melrose, forming the well-marked cliffs at Newstead, which may 
also have been the boundary of a fresh-water lake, whose depth depended on the 
height of the rocky barrier. The remarkable promontory of Old Melrose, nearly 
three miles below the present village, and the picturesque site of the original 
abbey of that name, founded, as is stated, in the end of the sixth century, is 
unquestionably owing to the prolongation of the trap-formation of the Eildons, 
which here becomes very narrow, crossing the Tweed just below Gladswood, and 
probably uniting itself to the trap of Bemerside Hill. The greywacke strata may 
easily be traced on each side of the narrow belt of trap on which the mansion- 
house of Old Melrose stands. 
If we now return to the little basin of the village of Melrose, close under the 
north foot of the Eildon Hills, we find the following arrangement of the rocks, 
the understanding of which will be facilitated by the inspection of the map, 
Plate VIIL., fig. 3, where the outlines of the formations are marked, and reference 
is made by numbers to the principal specimens, and by lines to the strike of the 
strata, where it has been observed. 
In the course of a little stream passing through the town of Melrose, called 
Matty’s or Dingleton Burn, the greywacke strata may with care be observed 
almost continuously; and it is remarkable that they exhibit the east and west 
strike* and vertical dip with scarcely any alteration until we approach the 
farm-house of Dingleton Mains, when they become suddenly much confused 
at the point marked 3. In the field above Dingleton farm occurs a quarry of 
felspar porphyry, including much quartz (specimen M. 4a.+). This seems to be 
an offset from the trap of the north-east Eildon Hill, the greywacke appearing 
higher up (at 5 and 6) nearly unaltered, and may be traced almost to the head 
of the small streams which rise between the Eildons, and afterwards join the 
Dingleton Burn. It has probably not been suspected that so large a portion of 
this face of the Eildons is formed of the rock of the surrounding country. The 
greywacke skirts the base of the principal Eildon Hill, the portion with the por- 
phyry passing a little to the south of a water-tank on the moor, near the point 
marked 17 on the map, where the position of the strata is east by north, and 
vertical. From this point the junction trends round the north slope of Bowden 
Muir, until we reach Cauldshiels Loch, on the Abbotsford property, where the 
junction is well marked on the eastern bank. 
* The deviation from true east and west is less than 5°. 
+ The collection of specimens referred to in this paper has been placed in the Museum of the 
Royal Society of Edinburgh. 
' 

