Notices and Extracts from the Minutes of the Geological Society. 165 



descending-, so that it is probable that at greater deptlis they may be united to 

 form a single vein. 



When I visited this mine, at the end of August 1820, water was so abun- 

 dant in the vein, that it had been found necessary to commence an adit for the 

 purpose of taking it off". There had then been shipped for Swansea about 

 forty tons of copper ore, estimated to be worth nearly 15/. per ton ; and there 

 were at the time above mentioned about twenty or thirty tons ready to follow 

 that which had been sent away. This produce is rather remarkable in propor- 

 tion to the extent and cost of the work ; it being* unusual to iind copper in 

 abundance so near the surface ; and when it occurs in this manner, it is not 

 deemed by miners a good omen of its continuance in depth; — but this opinion 

 is not much to be relied on, as there are many mines which have proved very 

 productive where the ore has been so situated. The ores were rich, and of a 

 mixed character, containing- the yellow and coated varieties of copper ore, with 

 some green carbonate 



4. Extract from a Letter from Mr. William Jack to H. T. Colebrookc, Esq. 

 v.p.G.s. &c. containing a Notice respecting the Rocks of the Islands of 

 Penan g and Singapore. [Read December 15, 1820 ] 



You will receive with this letter specimens of the rocks which occur in the 

 islands of Penang and Singapore, at the western entrance of the straits of 

 Malacca. The island of Penang- is entirely composed of granite, varying 

 considerably in the fineness of the grain, and sometimes containing horn- 

 blende, or becoming what would be called syenitic. 1 have sent one specimen 

 w hich contains very large and perfect crystals of hornblende and felspar. 



At Singapore the rocks are secondary. The principal one is a red sand- 

 stone, whose strata have a very considerable dip to the south or south-eastward. 

 This changes, in some parts, to a breccia or conglomerate, containing large 

 fragments and crystals of quartz. Strata of a slaty clay, which becomes soft 

 by exposure to the weather, often accompany the sandstone ; and an alluvial 

 bed of clay occurs in the channel of the river adjoining the town. A small 

 hill in tlie same neighbourhood is composed of an argillaceous ironstone. 



These appear to be the prevailing minerals along this side of the Malay 

 peninsula, and throughout the islands which lie at its southern extremity. 

 The central ridge is probably primitive. The sand.stone seems (o be the 

 chief secondary rock ; and the ironstone, 1 have mentioned, occurs abundantly 

 along the whole line of coast. 



