PKACII : NOTES FOI{ TJIE FIKLD KXCUUSION TO MKLHOSK. 
arranged in the long cliain-like rods. The rocks are varieties 
of trachyte. Those of the Mid Eildon contain riebeckite. A 
plat}^ structure is very conspicuous in some of the pipes and 
masses between the Mid and the Western Hill. This is due 
to the felspars being oriented in the direction of tlie flow of the 
material. A detailed description of the petrograpliical characters 
of these rocks is given l)y ]Mr. T. Barrow, now of the Geol. Sur. 
of Egypt, in the Geol. Mag. for 1896, page 371. He was the 
first to detect riebeckite, nepheline, and aegerine in them. He 
came to the conclusion that tlie rocks capping the Eildons are 
remnants of lava flows once continuous with those of the Black 
Hills of Earlston. With tliis conclusion I do not agree. The 
sheets are transgressive across the underlying Old Red strata. 
A similar sheet is found at a lower level in the Upper Old Red 
Sandstone on the East Eildon, which not only is transgressive 
from the Silurian rocks into the Upper Old Red, but alters the 
strata above it as well as below. 
A small outlier from the Eildon sheets is found in a quarry 
on the side of the Bowden Road, three-quarters of a mile to the 
west of the Eildons. 
Large vertical dykes of the plat}^ fluxion trachytic rocks 
are found on Coldshiels Hill, 2h miles south-west of Melrose. 
A very fine example of trachj^te or rhyolite dj^ke, showing 
splierulitic structure and beaded fluxion structure, is well seen 
near the head of the Rhymers Glen, where it is intruded into the 
Silurian rocks close to the outcrop of the Moffat Graptolitic 
black shales. This glen also gives a very good section through 
the great " ash neck," also of LoAver Carboniferous age. (See 
Fig. 3.) The walk through the Rhymers was a favourite one 
of Sir Walter Scott's. 
Eastward from Melrose there are several intrusions of this 
acid type. The chief, however, is that of the Black Hill of 
Earlston, three miles E.N.E. of Melrose. The rocks here are 
described in Mr. Barrow's paper already referred to. The 
rock is a sanidine trachyte. This rock is plainly intrusive. 
It can be seen in the quarry which yields the good specimens 
of Holoptychius nobilissimus, where it cuts across the overlying 
strata and alters them . 
