j 84/.J including Notices of Sumatra, the Malay Peninsula, fyc. 539 



assumed under the level of the sea, and then the whole tract of land 

 from which the hills spring, elevated by one movement, or is it more 

 probable that before the hills were upraised the general level of the 

 land was the same or nearly the same as it now is, and the hills con- 

 sequently obtruded from that level in whole or in part in the air ? The 

 action of the waters of the sea in spreading out the materials brought 

 to the surface by volcanic forces might seem an obvious explanation of 

 some of the facts formerly noticed. But if this cause be admitted at 

 all, its operation must have been transient and limited, otherwise the 

 surface accumulations on the different hills and parts of the same hill 

 would not have retained their striking local characters.* If the agency 

 of the sea is to be admitted, the most probable hypothesis, with our pre- 

 sent information, would be, that when the process, which dislocated and 

 pushed up the strata in different places into hills, began to operate, the 

 general level of the sea bed was much lower than it now is, and that the 

 same action caused its general elevation. In this way the surfaces of the 

 hills may have emerged so gradually from beneath the sea as to admit 

 of a partial action of its waters on their summits and sides during and 

 subsequent to the eruptions of matter, and yet not so slowly as to give 

 time for such extensive denudation as to obliterate the local peculiarities 

 of the ejected substances. My own opinion at present is, that all the 

 phenomena may be accounted for by purely volcanic, succeeded by 

 ordinary meteoric causes. At one time rock fragments and semi-fused 

 matter would be voided, heaped up at particular places, or ejected into 

 the air and showered over the surface. At another time, when the heat 

 was less intense or when steam or gases, not ignifluous or melted matter, 

 burst out, masses of soft clays and sandstone might be disembowelled 

 and spread over the bed of fragments. At other places the rocks might 

 be broken and pulverized in situ, and receive a considerable vertical 

 pulsion so as transiently to form an incoherent and agitated mass, espe- 

 cially towards the surface, but without the fragments or sand being 

 freely projected into the air.f 



* See ante page 527, Diluvial liypothesis- 



f Whether the mechanical action by which the hills were upraised long- preceded, 

 or was accompanied or soon followed by, semi-volcanic action in the most intense degree 

 which it here attained, or rather whether the semi-volcanic emissions and eruptions- 

 continued during- a long period to find vent through the fissures formed when the hills 

 were elevated, is a question that must lie over for the present. It is probable that they 



