1S47-J including Notices of Sumatra, the Malay Peninsula, fyc. 535 



wot concentrated at one or two points, and of comparatively great 

 power, so as to form regular craters of eruption or to elevate rocks to 

 a great height, but that they extended over a considerable area, and 

 that their intensity and mode of action varied greatly at different places. 



Amongst the most common volcanic products is one, small in size, 

 and varying in its character from common indurated argillaceous and 

 lithomargic, to porcellanous and jaspidious, which occurs in very singular 

 forms, vermicular, pseudo corraloidal, columnar,* and frequently resem- 

 bling pieces of ginger root, externally smooth, granulated, corrugated, 

 reticularly fibrous, &c. These are the compact forms, but there often 

 occur vesicular, or rather rudely ramose cavities descending between 

 the short thick irregular branches towards the centre, the branches 

 being themselves also sometimes perforated. 



Another product is a small smooth faintly shining black stone like a 

 fine gravel. 



At other places a gravel similar in shape but with a brownish or 

 chestnut-coloured coat or enamel occurs. These latter products may 

 readily be mistaken for water worn gravel, especially as they often 

 occur in broad thin beds, but on closer examination it is clear they are 

 of volcanic origin. 



All the various forms of ejected substances met with are due, I con- 

 ceive, in some degree to differences in the original mineral ingredients 

 of the rocks, but chiefly to the inequality of torrefaction, and the 

 circumstance of the heated, fused or semi-fused substances cooling in 

 the air or in mud or loose sand or clay. 



At an early stage in my inquiries I was led to think that the causes 

 of the eruptions were in part what have been called pseudo-volcanic, 

 and if coal shall be discovered it will then become a question whether 

 many of the geological phenomena of Singapore are not due to volcanic 

 action giving rise to and accompanying the conflagration of coal beds. 

 This would account for the paucity of proper volcanic products at the 

 surface, and the abundance of merely altered fragments agreeing in 



* Amongst the common large slags which are generally of irregular rounded shapes, 

 I have occasionally seen one agreeing in form with those small columnar stones and 

 externally rugose and roughly fibrous. In lactone may say it is the same as one magnified 

 in bulk from a few cubic, inches to 10 or 15 cubic feet, and with all its characters rendered 

 '•nurse in proportion. 



1 A 



