THK HAKTKKN AIU'HIPELAGO. 



141 



lambs and lai^lu-r i. alli-v^. nU-n <•[ j_rr>^it extent, diifvr imi.'li in tlnir 

 natural features, some being furest-clftd and extremely fertile, others 

 arid and destitute i>f timber. Sueh equally is the already described 

 Pertibi plain in the Rati a country, the aridity of tin's and other tract* 

 being no doubt due to the great elevation of the western highlands, 

 which arft in «ome place* lofty enough to intercept the min-hearing 

 cb»uds . rnlling up fn >in the Indian Ocean during tlas south -western 

 monsoons, A» might be expected, llits parched lands occur especially 

 in the north-east, where the m^nn elevation of the western, range is 

 greatest, ami where the uplands of the Malay Peninsula again fnnn 

 a lmrrii«r against the tnnfci tire-laden clouds from the China Sea, 

 Hence, llI*>, in the northern lowland* the intently heated dry rdr 



Im'.-i.idms ratified ;L ud repLced by ! i-r :u sit: - |ili» ri'- mrr-uK causing 



violent local disturbances, and generating those sudden gusts and 

 squalls knuwn as * Sumatra;*," which are so dangerou* to navigation 

 in Ae Strait of Malacca. 



Rivers — Owing to tliu westerly position of the* upland!!, and a 

 general easterly tilt of the landfall the large wuiert'onrsi-s necessarily 

 flow in the direction from west bi east. On the west sade the only 

 important river is the Singled, which develops a winding course 

 through the Aehin and Singkel districts to the north -west coast over 

 against the l?anyak Islands, lhit on the opposite side a large numher 

 of considerable streams make their way fnnn the western ranges 

 across the lowlands eastwards to the CJhina Sea, Ap the island 

 broadens perceptibly southwards between 2° N. — 4* S f hit., so the 

 rivers increase in amplitude in the same direction, the largest being 

 the Sink and Indrugiri respectively north and south i*f the equator, 

 the J.liilIil, aSw.ut "T S., mid the Palembang (Mu-i\ most voluminous 

 of al I, bet ween 3* — 5* 9. All are navigable for vessels of considerable 

 size, although somewhat obstructed by shoals, ban?, and intricate 

 deltas about their lower course. Their nun tenuis headwater?, con- 

 verging from various points on the main stream, give them a fan- 

 slicipe.il appearance, and cauae extensive 11 codings of their low -lying 



batiks during the rainy season. The Siak, one of the meal useful for 



iiavigiilih' purposes, is accessible \o Inrgi- vessel* fur HO, to ships of 

 200 toM for 100, and to boats for 150 mile* fnnn its mouth. But 

 the Pahmhang with its great tributaries, the Rawos on it« left, the 

 Ldiiuatang ami Ogan on its right bank, presents a far more exlen-n b 

 water system, naviguSed fur nmiim' hundred mill -, v-|u-idally by large 

 bamboo "rakit-V 40 feat and upwards in length. On one of ihese 

 rafls Mr. ML O. Forbes in 1881 llnated duwn the Rawas from Pulu- 



