
XL—Notes on the Geology of the Eildon Hills, in Roxburghshire. By James D. 
Forses, Esq., F.R.S., Sec. R.S. Ed., Professor of Natural Philosophy in the 
University of Edinburgh. 
(Read 7th April 1851.) 
The following remarks, being the result of a careful examination of a small 
district of country characteristic of the relations of the trap formations, are per- 
haps worthy of being recorded; although the general features of the county of 
Roxburgh have been very clearly stated in a paper by Mr Minne, published in 
the 15th volume of the Edinburgh Transactions. 
The outburst of porphyritic trap forming the conspicuous small group of the 
Eildon Hills, may be stated to be surrounded by the characteristic greywacke of 
the south of Scotland. It forms an elongated patch on the map, extending from 
the west end of Bowden Muir in the direction of the town of Selkirk, and running 
from west-south-west to east-north-east (true) towards Bemerside Hill, on the north 
bank of the Tweed. The breadth is variable, probably less than is generally sup- 
posed ; but it cannot be accurately ascertained, owing to the accumulated diluvium 
which covers the whole south-eastern slope of this elevated ridge. On this ac- 
count, my observations on the contact of rocks have been almost entirely confined 
to the northern and western boundaries of the trap, although the other side was 
examined with equal care. 
The character of the greywacke strata near Melrose is in general that of the 
surrounding country. The strike is nearly due east and west, the position nearly 
vertical, rather declining to the north; and these features are remarkably uniform 
and uninterrupted. In the excellent sections exhibited by the course of the rail- 
way, immediately to the east of Melrose, where the greywacke is not far distant 
_. from the trap of the Eildon Hills, the strike of the strata inclines more to the 
south-west, the strata are thinner and more undulating, mixed with more numer- 
ous clayey strata, and including many veins of calcareous spar. If we follow the 
greywacke strata to the eastward, we find them exposed near the village of New- 
stead, and along the south bank of the Tweed towards Drygrange Bridge. Be- 
tween these two points they are so much altered as to be scarcely recognisable, 
yet having the usual stratification from east to west. There is every appearance 
of a real barrier having crossed the present course of the river, which still runs 
in a very uneven channel; and behind this barrier is an enormous accumulation 
of debris of all sorts, forming the eminences through which the railway passes, 
beyond the village of Newstead, which have no nuclei of solid rock, as far as can 
be seen. Among these debris, boulders of the trap tufa of Melrose are conspicu- 
VOL. XX. PART II. 31 
