Vol. 50.] AND OTHER ASSOCIATED ROCKS AT BARNTON. 43 



and about 2| furlongs from tho ' picrite '-cutting on the Barnton 

 Railway. 



My Corstorphine Hill specimen resembles to a certain extent tho 

 specimen from the vein running through the picrite which has just 

 been described. In both cases there are augite-crystals particularly 

 well preserved, and in both the felspar is largely replaced by some 

 other mineral ; but whereas in my railway-cutting micro-section 

 some felspar-crystals are seen showing twin-striation very clearly, 

 there is not one in the Corstorphine Hill micro-section — so complel e 

 is tho alteration of the felspar in that rock. Mr. Allport, however, 

 mentions that in micro-sections from some parts of Corstorphine 

 Hill a little plagioclase is preserved. The brown dichroic mineral 

 of the rock from the railway-cutting seems absent from the Cor- 

 storphine Hill specimen. I am not certain as to pscudomorphs 

 after olivine in the railway-cutting specimen, but they undoubtedly 

 occur at Corstorphine Hill ; and there are some pale-green aggregates 

 of a fibrous or radial structure, forming plates into which the felspar- 

 crystals penetrate as in an ophitic dolerite. Probably they represent 

 a pyroxene, now replaced by actinolite and serpentine. 



The remaining cuttings on the Barnton Railway showed Boulder 

 Clay, the boulders being few, but large. 



In conclusion, I must express my indebtedness to Prof. Bonney 

 for kindly looking at the micro-sections and for assistance generally. 

 He allows me to say that he agrees with the determination of the 

 minerals mentioned in this paper. 



Discussion. 



Sir James Maitland said that he had on several occasions visited 

 the section described, and had seen the paper from which some 

 extracts had just been read. The ' calm ' or indurated shale in 

 connexion with the intrusive igneous rocks at Barnton was very 

 like that which occurred to a depth of 36 feet in a similar relation 

 to the basalts of Sauchie (Stirling). Other things of interest were 

 found in the Barnton cutting : for instance, a heap of recent sea- 

 shells was cut through about the 170-feet level, the same level as 

 that of the large boulders resting on patches of sand described in 

 the paper: and a short distance west of Barnton he had found good 

 oil-shale forming practically the top of the solid geology, and covered 

 with over 100 feet of alluvium. The six-inch map hung on the 

 screen was an old one, and did not show an intrusive sheet of basalt 

 to the east and north of Craiglcith, which separates that famous 

 quarry from an excellent bed of building-stone proved during the 

 last month to a depth of 45 feet. 



