578 GEOGRAPHICAL NOTES IN MALAYSIA AND ASIA, 



area. While the ranges and mountains connected with the craters 

 are necessarily of a barren rugged character on their summits, 

 their lower declivities, which are covered with a luxuriant vege- 

 tation, produce by their drainage a soil of unexampled richness 

 and depth. Thus the country surrounding Surabaya surpasses 

 any in Java for the extraordinary fertility of its soil. Hence the 

 crowded population and the riches of the agriculture. The origin 

 of the soil, its phy.sical structure and its liability to inundation 

 must necessarily, in such a climate, be unfavourable to human 

 life. Cholera and fever seem never to be absent from this part of 

 the country, affecting the natives and Europeans alrcost equally. 

 To the west of Surabaya the physical structure of the countiy 

 alters. Here for the first time we meet with an extensive moun- 

 tain range, which, though volcanic in character, has not any 

 extinct crater for 100 miles or more. The basement of this range 

 may possibly be on a line of fissure whence volcanic emanations 

 arose in the form of craters which have disappeared by weatliering. 

 There are but few places where I had an opportunity of examining 

 these beds, and all I saw was decidedly volcanic. But the face of 

 nature has been so scored and changed by the system of irrigation 

 which prevails, that unless on the very mountains themselves there 

 is nothing for a geologist to see. The range runs almost east and 

 west, with a very slight inclination northward at its westein end. 

 There are several parallel spurs with other subsidiary ranges at 

 right angles. It is deeply scored by valleys of ero.sion, on the 

 sides of which is an alluvial or coarse gravel formed of volcanic 

 material. The west side is bounded by the valley of the Serang 

 River, and through this the railway takes its course. All along 

 the south side the river Solo has a very winding channel, following 

 exactly the curves of the .spurs from the mountain range, and 

 flowing in a generally east direction. 



Madiun. — At about half the length of the range it is joined 

 by the Madiun, a tributary nearly as large as itself, and then the 

 united streams flow through a narrow and very remarkable gap 

 in the range, and take a cour.se north, nortli-east, and then finally 



