THE ISLANDS OF THE BAY OF BENGAL. 43 



of Java, which I had myself the opportunity of studying and com- 

 paring in their distribution and lithological character. These 

 became first known through the late Er. Junghuhn, whose researches 

 on the physical geography of Java are of such merit. 



" According to the reports of the Dutch Mining Engineer, 

 Huguenin, a repetition of the geological formations of the Nicobars 

 appears to be met with in the Tjiletuk Bay (the southern lateral 

 bay of the Wynkoop Bay on the southern coast of Java). The 

 prevalent formations) here are sandstone-conglomerate and highly 

 developed greenstone-breccias, besides plutonic rocks of the green- 

 stone group. From specimens which I had an opportunity of 

 seeing in the local collection at Beutenzorg, I found that these 

 plutonic rocks are serpentines, gabbros, and aphanites, exactly 

 similar to those of the Nicobars. Equally identical with those 

 occurring on the Nicobar Islands, appear to be the chalk-white 

 clay-marl in the middle portion of Bantan, and the fine white 

 marls in the southern portion of Tjidamar, mentioned by Junghuhn. 



" I suspect that to the upper Miocene group of Java correspond 

 the tertiary deposits of the Nicobars, although fossils confirming 

 the suggestion have yet to be discovered. It is also beyond doubt 

 that these deposits are not wanting on Sumatra, in certain respects 

 a connecting link between Java and the Nicobars. Junghuhn 

 (Jog. cit., p. 8) justly remarks : — ' The tertiary formation appears 

 to have a sub-marine extent over the whole of the Indian Archi- 

 pelago, because wherever within this Archipelago the earth's sur- 

 face rises above the level of the sea, this Neptunian formation is 

 observable. I know this for certain as regards Northern Sumatra, 

 where the tertiaries are especially found in the Batta districts 

 (Battalandern). With the exception of the trachytic island 

 Dungus Nasi all the islands in the Bay of Tapanuli (situated 

 exactly in the prolongation of the Nicobars), besides the adjoin- 

 ing low shores of Sumatra, and partially also the mountains near 

 Tuka, are composed of more or less upheaved sandstone strata, 

 containing, though sometimes rarely, tertiary shells.' Thus it 

 appears to be principally on the southern coast of Java and the 

 south-west coast of Sumatra that we find a repetition of the geo- 

 logical conditions of the Nicobars. 



" The commencement of the eruptive formation is in Java in- 

 augurated by serpentine, gabbro, massive rocks resembling diorite 

 (greenstone trachytes as in Hungary) ; more or less typical trachy- 

 tic rocks follow, and the grand volcanic eruption, extending up to 

 the present time, forms the termination of the enormous eruptive 

 phenomena in the Indian Archipelago. At the same time it 

 appears that the eruptive line has been shifted slowly on Java from 

 S. to N., and on Sumatra from S. W. to N. E., so that this line 

 would strike east as regards the Nicobar group in the same longi- 

 tude in which east of the Andamans it re-appears on the volcanic 

 Barren Island and Narcondanx. 



