612 MR. A. K. C00MARA-SWAMY ON [Aug. I9OO, 



The graphite mined at Mawatakelle and Deldahawatte in the 

 same district, and at Godaduwa near Galle, I believe also occurs 

 in veins. 



We see, then, that the Ceylon graphite occurs chiefly in this way, 

 and not in beds or lenticular streaks. When, however, it occurs as 

 a rock-forming mineral (as, for example, in a specimen from 

 Hakinda described on p. 595), it is present in small specks and 

 scales, scattered through an igneous rock in quantities too small to 

 repay the cost of working. In these cases it may be supposed to 

 have consolidated from igneous fusion, bearing in mind the well- 

 known occurrence of graphite as a furnace-product, and in meteorites. 



It seems impossible to regard the vein-graphite as the highly 

 metamorphosed remains of an ancient flora or fauna. The high 

 melting-point of graphite and other considerations make it unlikely 

 that the veins arose as dyke-like intrusions of molten graphite. 

 Prof. Moissau ' suggests that graphite may have crystallized out of an 

 iron-maiima, the iron having been subsequently removed chemically, 

 but here no traces have been found of the immense quantity of iron 

 that would be required for this process. Moreover, the included 

 rock-fragments and the portions of the matrix next the veins would 

 have been considerably altered by the high temperature required. 

 It seems likely that the formation of these graphite-veins has not 

 been associated with very extreme temperature at the point of 

 deposition of the graphite. 



l)r. Diersche [30] p. 287 suggests that the graphite may have been 

 introduced in liquid hydrocarbons (such as petroleum, naphtha, or 

 asphalt) which were reduced in situ. These liquids, rich in carbon, 

 might have been introduced either from above or below. 



Slightly different is the sublimation-theory of Prof. Walther [18], 

 who refers to the occurrence of a graphite-like substance which is 

 deposited in the flues of gas-works. He supposes, not that the 

 carbon itself was sublimed, but that it was deposited in the veins 

 from sublimed hydrocarbons. 



Two hypotheses thus seem to be plausible, both involving the 

 existence of suitable hydrocarbons : (i) the liquid theory of Diersche; 

 and (ii) the gaseous theory of Walther. Each may be right in 

 different eases, and neither presents any insuperable difficulty. The 

 association of graphite, quartz, and calcite at Mlhene is, I think, in 

 favour of the liquid theory ; so too, perhaps, the slight impregnation 

 of included rocks noticed at Ragedara. 



Y. Literature. 



1" 1621. Davy, John. ' Travels in Ceylon.' London, 4to. 



2] 1847. G ygax, Rudolph. ' On the Mineralogy of Ceylon ' Joum. Roy. Asiat. 



Soc. Ceylon Branch, vol. i, No. 3, pp. 1-5. 

 [3] 1848. Gygax, Rudolph. 'Report on the Geology & Mineralogy of the 



Sabaragamuwa District.' [Pari. Reports.] 

 [4] 1848. He>'derso>-, Lieut. 'On Ceylonite found near Trincomalee ' Journ. 

 Roy. Asiat. Soc. Ceylon Branch, vol. ii, No. 4, pp. 97-99. 



1 Comptes-rendus Acad. Sci. Paris, vol. cxx (1895) p. 17. 



