590 MR. A. K. COOMARA-SWAMY ON [Aug. 1900,- 



31. On Ceylon Rocks and Gkaphite. By A. K. Coomara- 

 SwAiir, Esq., F.G.S. (Eead June 6th, 1900.) 



[Plate XXXIII.] 



Contents. 



Page- 



I. The Physical Geography of the Area 590 



II. The Kecent Deposits 591 



III. The Crystalline Rocks 592 



IV. The Graphite ; its Mode of Occurrence and Origin 609 ' 



V. Literature 612 



VI. Summary 613 



I. The Physical Geography of the Aeea. 



Ceylon is almost connected with India by the Manaar and Kames- 

 waram Islands and the reef known as Adam's Bridge : there is no- 

 channel deep enough for large steamers to pass. Nearly four- 

 fifths of its area is a flat ; low country ' forming a maritime belt 

 in the south, and covering a greater area in the north. The main* 

 mountain-massif, consisting of ancient crystalline rocks, is situated 

 a little south of the centre of Ceylon in the South Central, Uva, 

 and Sabaragamuwa provinces. In this area rise lofty and often 

 precipitous mountains, of which the highest is Pidurutalagalla, 

 8290 feet above sea-level ; while Adam's Peak reaches 7353 feet. 

 In between these peaks stretch considerable tracts of tableland or 

 rolling grassy plains (Patanas), such as the Newera Eliya Plain, 

 at an altitude of 6200 feet, or the Elk and Horton Plains, over 

 7000 feet. The rainfall in these districts may exceed 280 inches 

 per annum, while it is only 50 inches in the northern flat, dry 

 country. The rivers rise in the mountainous districts, running 

 at first through rocky gorges, forming striking waterfalls, but 

 meandering slowly through alluvial flats when they reach the low 

 country. 



Ceylon is essentially a continental island, and, as we should 

 expect, shares to a great extent the flora and fauna of India. It 

 is, however, remarkable that nearly 30 per cent, of Ceylon phanero- 

 gams are endemic, and the same is true of 2 per cent, of the genera 

 [13]. 1 This fact indicates a not very recent separation from 

 India, indeed it is evident that Ceylon has risen in quite late 

 geological times. This is shown by the extensive areas of recent 

 marine deposits which are found fringing the coast, and in the 

 north covering a larger area. Probably the same is true of Southern 

 India. A depression of a few hundred feet affecting Ceylon and 

 Southern India would submerge much of the low country (which 



1 The numerals between brackets throughout this paper refer to the biblio- 

 graphical list on p. 612. 



