9G SKETCH OF THE PHYSICAL GEOGRAPHY 
Plutonic Pocks.— 1 Throughout the whole length of the Penin¬ 
sula plutonie rocks have swollen up, and they are so abundant that 
authors have desciibed the interior of the country as presenting a con¬ 
tinuous range of “ primitive” mountains. Our own observations do 
not lead to the conclusion that the Peninsula can be considered as a 
great longitudinal plutonie ridge, with the purely sedimentary rocks 
regularly disposed in strata on the two sides, those on the west dipping 
away from it in that direction, and those on the east in the opposite 
direction. On the contrary, a multitude of phenomena satisfy us that 
the sedimentary rocks themselves have everywhere, in a greater or less 
degree, been subjected to direct plutonie induence in a manner that 
has not hitherto been noticed. The mode in which the granitic and 
allied rocks occur at a distance from the central ranges might of 
itself suggest the true theory of the region. 
It appears to us that the Peninsula, in its whole breadth, is one of 
the hands of more intense action in a great region which has been 
subjected to plutonie intumescence. The mountainous central tracts 
indicate that the intumescence was in general greatest there ; but the 
irregularity with which the granitic ranges occur, their distance from 
the middle of the zone in many cases, the occurence of plutonie 
patches on the outskirts of the zone amongst the sedimentary rocks, 
and of the latter in the more central tracts, finally, the fact of-bold 
plutonie mountains abruptly appearing at the very edge of the zone 
and even beyond it, such as Pinang, the Karimons, Pulo Tioman, 
Sec. are inconsistent w r ith the simple theory of a plutonie ridge rising 
in the centre of the Peninsula like a long wedge, and raising the 
strata on either side. 
The general uniformity in the direction of the Peninsula proves 
that the subterranean intumescence itself, in its greatest force, had the 
same uniformity of direction. It has swollen up in a zone, approach¬ 
ing, in its horizontal section, nearly to a very elongated parallello- 
gram, having the direction of S. E. by E. 
While expanding it must therefore have produced a great tension 
in a transverse direction, and whether, in the result, the crust had 
given way in one great rent down the middle of the zone, or in a mid- 
