152 



GEOLOGY OF PULO PINANG, 



masses of granite are some with beautiful veins and imbedded crystals 

 of quartz, and prismatic crystals and amorphous portions of hornblende? 

 (No. 5). Specimens of these, of good size, were, with difficulty, broken 

 off ; and indeed to shew them in perfection, it would be requisite to carry 

 away the rolled masses entire. No. 6, is a specimen of the granite found 

 opposite Saddle Island, of moderately fine grain, and containing a large 

 proportion of mica. On the south-west the granite, containing a large pro- 

 portion of felspar and quartz, is nearly of a whitish colour — ^(No. 16). At 

 night, from reflecting the moon's rays, it is observed to glisten at the dis- 

 tance of more than a mile. Imbedded in it, we found a globule of fine 

 grained black granite, containing abundance of mica (No. 17). The whole 

 of the south side of the Island is composed of a coarse brownish granite 

 (No. 18). On the south-east point opposite Pulo Rimau, it occurs again 

 of a grey colour (No. 19). These difierent varieties found along the 

 coast, occur also in the body of the mountains, and it has therefore been 

 considered, unnecessary to transmit specimens taken from the interior. 



* The east and south-west plains are entirely of alluvial formation, pro- 

 bably in great measure formed by the detritus of the mountains washed 

 down and collected through the lapse of ages. At first sight of the east plain 

 particularly, which juts in a triangular form into the narrow strait between 

 the Island, and the Quedah coast, and on which are built George Town, 

 the Fort, the various public buildings and the habitations of the English 

 residents, the geologist is impressed with the idea that the sea must have 

 at one time covered it and washed the base of the mountains. This is 

 confirmed in some measure by the phenomena observable on the opposite 

 shore of Quedah, where Captain Low has traced the successive deposits of 



* Some of the following remarks on the plains, rivulets, water, &c. have already appeared 

 in my " Contributions to the Medical Topography of Prince of Wales' Island," printed by the 

 Pinang Government. 



