680 MR. A. K, COOoMARASWAMY ON THE [Nov. 1902, 
36. The Pornt-pE-GatLe Group (CeyLon): WoLLAsTonITE-SCaPOLITE 
GyetssEs. By Ananpa K. CoomAraswAmy, Hsq., B.Sc., F.L.S., 
F.G.S. ‘(Read June 18th, 1902.) 
[Prats XXXIV—Matr. | 
I. Lyrropvuction. 
Pror. A. Lacrorx’ has recorded the existence of wollastonite- and 
seapolite-bearing rocks in Ceylon. The specimens examined by him 
can hardly, however, have come from Galle, as they contain garnet, 
a mineral never found in the rocks of the Galle Group described 
below. It seems therefore probable that rocks allied to those of 
Galle, but differing from them in petrological details, will be found 
elsewhere in Ceylon. 
I have on a former occasion’ given a short description of the 
Galle rocks, and am now able to supply a more detailed account 
of the rocks and to describe their field-relations. There are 
excellent exposures at Galle, within the Fort on the western side, 
between the Signal flagstaff and the north-western bastion ; outside 
the Fort beiow the north-western bastion; and south-west of the 
Victoria Park near the remains of an old powder-magazine. All 
these exposures can be easily visited in the course of one whole day 
spent at Galle. 
Il. Generat Description. 
The Galle rocks differ from normal types belonging to the 
Charnockite Series in the following ways :— 
(1) The presence of wollastonite, scapolite, and sphene. 
(2) The existence of definite dykes and segregation-veins crossing the foliation. 
(3) The absence of garnet, hypersthene, mica, and original hornblende, and 
bands of ‘ granular quartz-rock.’ 
(4) Somewhat coarser grain. 
But resemble them closely in 
(1) The variability of chemical and mineralogical composition. 
(2) The conspicuous mineral-banding (foliation). 
(3) Common strike (about 10° west of north). 
(4) The petrological characters of the acid types (especially as regards the 
felspars). 
(5) The local tendency to graphic structures. 
1 ‘Contributions 4 l’Etude des Gneiss 4 Pyroxéne et des Roches & Wernerite’ 
Bull. Soc. Minéral. Franc. vol. xii (1889) p. 269 & pl. xii, fig. 2. 
Pe foe Rocks & Graphite’ Quart. Journ. Geol. Soc. vol. lvi (1900) 
p. : 
