532 On the Local and Relative Geology of Singapore , [June, 



appearance ; congeries of curved, zigzag and radiating veins in sand- 

 stone, clays and shales, filled with crystallizations, and both from their 

 own appearance and the alteration in the rock in which they are found 

 showing chemical or electrical action of a volcanic nature ; the presence 

 of sulphur accompanying anthracite in shales denigrated and rendered 

 fuliginous by fire ; the slaggy appearance of many rocks and fragments 

 which are often covered externally by a shining black, bluish-black, 

 or dull iridescent varnish or glaze ; the scoreous appearance of others, 

 many being mere cinders ; the abundant presence of oxides of iron, and 

 particularly their intensity in those places where the other evidences of 

 igneous action are most marked, and their absence where these are 

 entirely wanting. It is impossible to refer these facts and others of 

 an analogous character, which will be mentioned in a future paper in the 

 description of particular localities, to any but volcanic causes. The 

 reddish, reddish-brown and reddish-black rocks which are found so 

 abundantly have been noticed by Lieutenant Newbold, Colonel Low and 

 others. The general name of laterite has been sometimes applied to 

 them. Colonel Low uses the terms "iron clay," " iron stone" and 

 " iron ore." The red soils have been in like manner called laterite or 

 iron soils. Both terms appear to be objectionable. Laterite is a parti- 

 cular species of ferruginous clay which indurates on exposure to the 

 atmosphere like many other rocks : it ought to be restricted to the clay 

 to which it was assigned by Dr. Hamilton, and not indiscriminately 

 applied to every new rock strongly marked by oxides of iron. With 

 respect to the term iron clay or clay iron stone, it has not yet been 

 shown that any of the proper argillaceous iron ores, into the composition 

 of which carbonic acid enters so largely, are found in Singapore. If 

 there are any they have been disguised and changed by heat, decompos- 

 ing into peroxides. The fact however is that these so called laterites 

 and iron ores, externally as to colour and form differing little if at all, 

 prove often on examination to be only fragments of the common strati- 

 fied rocks, sometimes calcined, sometimes indurated, and sometimes 

 partially fused by heat. We cannot therefore resort to a prevalence 

 either of laterite or iron ores to explain the geology of the Island, and 

 are by the rocks, which have been so designated, led back to volcanic 

 causes.* 



* Laterite. — Many'of the clayey hills here appear to me to be decomposed sienite, some- 

 tones unaltered by supervening- volcanic action, but generally partaking- in the metamor- 



