■598 MR. A. K. C00MARA-SWAMY Otf [Aug. I9OO, 



(3) Diorites. 



These were noted at Ambalangoda and Kandy. They are 

 -dark rocks with a characteristic 4 pepper-and-salt ' appearance. 

 The varieties include normal diorites, and quartz- and quartz- 

 hypersthene-diorites. The structure is granular; where foliation 

 is present the quartz-grains may be elongated. The hornblende 

 is often partly derived from the pyroxene. 



Ambalangoda. — The dark diorite here is apparently intrusive 

 in gneissose rocks. It is well seen on the shore opposite the rest- 

 house, where it is traversed by fine felspathic grains, and it occurs 

 in a dyke-like manner in the quarry on the first little promontory 

 south of the river, south of the rest-house. The minerals are horn- 

 blende and plagioclase (2Q° 29°, probably labradorite) with a little 

 luotite, apatite, and zircon. Brown -stained and greenish decom- 

 position-products are occasionally associated with undecayed frag- 

 ments of a pyroxene, which they appear to represent. Quartz is 

 absent : the rock is a normal diorite. 



Kandy. — A dark-banded rock occurs in the quarry between the 

 lake and the reservoir, associated with the more abundant white 

 normal granulite. The foliation in the diorite is due to alternations 

 of hornblendic with purely quartzose-felspathic bands. The minerals 

 are plagioclase (20° 21°, probably labradorite), hornblende, quartz, 

 scarce biotite, magnetite, apatite, and zircon, and also a little 

 decayed pyroxene. The rock is a quartz-diorite. 



A very dark diorite is seen in the quarry on the Pallekelle side 

 of the ferry, below Kandy. The minerals are as in the last rock, 

 but a considerable amount of hypersthene is present : the foliation 

 also is similar. This rock is a quartz-hypersthene-diorite. 



(4) Dolerites. 



Ohiya. — A specimen from the railway-cutting near the first 

 tunnel above Ohiya Station is a hornblende-biotite-dolerite, con- 

 taining plagioclase (probably labradorite), hornblende, biotite, augite, 

 hypersthene, magnetite, pyrite, apatite, and zircon. The altera- 

 tion of the pale augite into dark hornblende, commencing along the 

 cleavage-traces, is well seen. 



H or ton Plains. — A similar rock, collected about 1000 feet 

 higher, near the Horton Plains rest-house, is a hornblende-hyper- 

 sthene-dolerite, containing plagioclase (23° 24°), hornblende, 

 augite, hypersthene, magnetite, and apatite. 



(5) Gabbro. 



Colombo. — Near the Battenberg Battery a dark rock, weather- 

 ing into large spheroidal masses, has been recently exposed. It 

 consists essentially of plagioclase (35° 36°, probably labradorite) and 

 pyroxene (sea-green augite and pleochroic hypersthene) ; hornblende 

 and biotite are abundant ; magnetite, apatite, and zircon are also 



