Vol. 70.] INTBUSIONS >~EAR MELROSE. 305 



that nepheline occurred somewhat freely in association with the 

 riebeckite ; but it seems unlikely that such is the case, for inter- 

 stitial quartz is present in most instances, and I have failed to 

 detect nepheline in the many specimens examined (both micro- 

 scopically and by staining). He also drew attention to the felsitie 

 texture characteristic of the Mid Eildon mass, and to the pre- 

 dominance of typical porphyritic trachytes in ' Easter ' Eildon 

 (North). He described the Black Hill, and both here and in 

 the North Eildon suggested the original presence of riebeckite. 

 He regarded the two masses as remnants of lava-streams of Old 

 Red Sandstone age ; but his own observations on the Black Hill 

 are strong evidence against such an interpretation. Following 

 this description, we find passing references to the igneous rocks 

 of the neighbourhood in the account given by Dr. Peach & 

 Dr. Home of the Silurian rocks of Southern Scotland. The 

 ' felstones ' are now spoken of as trachytes, and the main features 

 of the Chief swood neck x — its probable Carboniferous age and its 

 contents of greywacke and trachyte-blocks — are touched upon 

 briefly. Dr. Harker ~ has more recently figured a specimen from 

 the Mid Eildon as an example of riebeckite-orthophyre. 



It was evidently desirable to obtain a more comprehensive 

 knowledge of the petrology of the district, and with this end 

 in view the various exposures have been carefully examined, and a 

 large number of specimens collected and sliced. In the following- 

 pages the intrusions are considered in the order in which they are 

 cited on p. 303. 



The chief rock-types represented are : — 



(1) Quartz-trachytes. 



(a) Non-porphyritic: for instance, Bemerside. 

 (6) Porphyritic, Black Hill. 



(2) Sanidine-trachytes. 



(a) Non -porphyritic, Cauldshiels Hill, Whitelaw Hill, etc. 



f with fresh riebeckite, Mid Eildon. 

 n\ -p -u . ■ x • J with asgirine-augite and olivine, Mid Eildon. 

 ^ ' ' | without fresh ferromagnesian mineral, North 



I Eildon. 



(3) Fel sites, with fresh riebeckite, Eildon West and Mid Hill. 



(4) Quartz-porphyry. 



(5) Sanidine-porphyry. 



(6) Basalt, Little Hill. 



(7) Volcanic agglomerate, ash, etc. 



III. Laccolites axd Sills. 



The White Hill is covered with ploughed fields, and bounded 

 on the north-east and south-east by Upper Old Red Sandstone and 

 on the west by Silurian rocks, but actual contacts are not seen. 



1 Mem. Geol. Surv. 'The Silurian Eocks of Britain ' 1899, vol. i (Scotland) 

 p. 190. 



3 ' Petrology for Students ' 4th ed. (1908) pp. 128 & 129, fig. 33 B. 



T2 



