200 MR. J. PARKINSON ON THE GEOLOGY [May IQOIy 



individuals of the former scattered through the rock. The specific 

 gravity of such a rock is 2-82. 



One possessing well-marked bands has a peculiar, though quite 

 distinct foliation, making an angle of about 45° to the direction 

 of the bands. Under the microscope the rock is seen to consist of 

 plagioclase, orthoclase, quartz, green hornblende, a little brown 

 mica, zircon, and apatite : the darker minerals predominating in 

 certain parts, and, together with less quartz than in the remainder 

 of the slide, constituting the banding. The proportion of mica 

 varies, and in several instances it is associated with hornblende 

 in a way which suggests very strongly its formation from that 

 mineral. Iron-ores are abundant : for the most part they are 

 probably ilmenite, together with some pyrites. The rock shows 

 no indication of crushing, and the foliation referred to above seems 

 probably due to a fresh movement preceding final consolidation,, 

 causing the mica-flakes to take up a new position oblique to the 

 plane of banding. 



(b) On the Ceylon Government Railway: westward 

 from Kadugannawa. — Along the railway-line good but 

 monotonous sections are exposed, essentially resembling those just 

 described. The rock is both finely and coarsely banded, in some 

 places the granitic veins measure 4 inches across, and although they 

 frequently remain straight for some distance, yet they often vary 

 in thickness, thinning out, then swelling. Occasionally the rock 

 is gnarled, but this is not characteristic ; while not infrequently 

 the veins, by intersecting, produce an appearance of brecciation. 

 This seems incompatible with any theory which would impute the 

 banded structure to crush. A little farther west the rock, banded 

 in its lower part, has a much more brecciated look in its upper. 

 The whiter veins seem partly to enclose lenticular masses of the 

 darker rock, and, in a few cases, to form a. rather high angle with 

 the underlying bands. In one case a long band of the darker 

 rock, containing one or two small white bands, has been broken 

 in two (fig. 3), so that probably the granitic rock is not all quite 

 of the same age (fig. 4). Some coarse felspar-veins are certainly 

 younger than the granitic rock which constitutes the more regular 

 bands. 



The cross-cutting granite-vein of fig. 4 is fine-grained and white 

 in the hand-specimen, thereby differing from the granite described 

 on p. 199. A thin slice exhibits large and very irregular grains of 

 quartz, orthoclase in considerable quantity, microcline rare or absent,, 

 plagioclase, and a few greenish flakes of mica. The rock has a 

 granulitic structure, the quartz usually penetrating the felspar, or 

 in some places forming quartz vermicule. Its specific gravity 

 is 2-62. 



A dark band (of specific gravity 3*28) in the banded rock below 

 Kadugannawa shows in a thin section much pale-green augite, 

 altering to darker green hornblende. A brown mica is present, 

 often presenting the appearance of a further product of alteration,. 



