164 NOTES ON SUMATRA. 
whole formation is intersected in every direction by large veins, dykes, 
and masses of laterite, sometimes cellular, powdery, and ochraceous, 
but more frequently very hard, dense, and heavy, of a blackish-red co- 
lour, and containing 75 to 80 per cent. of iron, but probably also too 
much silex to be very valuable as an ore. These strata are very much 
disturbed, being inclined at high angles and in various directions, and 
often much curved and contorted ; consequently, though few of the islets 
rise more than one hundred feet above the water, their shores, when 
rocky, are very picturesque. Many however consist only of sand and 
broken coral, and not a few almost entirely of loose, waterworn blocks 
of very hard, heavy laterite, apparently left behind by the degradation 
of the strata in which it was enclosed. Many apparently small green 
islands are merely clumps of salt-water trees, such as the “ Bakau,” 
“ Tameno,” and “ Tunga,” all species of Rhizophora, the “ Pempat," a 
Sonneratia, and the “ Apiapi,” an ZEgiceras, growing upon a reef of 
mud and broken coral, exposed only atlow water. Numerous beds of 
coral are everywhere seen through the clear water glowing with all the 
eolours of the rainbow, and supplying at once food and shelter to the 
brilliant fish always seen among them. Most of these coral fish are 
furnished with numerous and strong teeth, and they literally graze upon 
the summits of the coral. They may be seen, as it were, rasping off 
ihe surface, and their stomachs always contain a large quantity of a 
pasty, calcareous substance, which is, I believe, the indigestible part of 
their food, to the peculiar nature of which they probably owe their 
sometimes poisonous properties. As might have been expected, I found 
many shells wherever I landed, and the air was enlivened by numbers 
of hawks, pigeons, terns, sandpipers, kingfishers, herons, and ibis, which 
find among these solitary islands the two great desiderata of plenty of 
. food and an undisturbed retreat. 
The vegetation of these islands is not very peculiar, being usually 
that. of the coasts generally in these latitudes. Rhizophore, Sonneratia, 
Aigiceras, and two species of a Combretaceous genus, one with scarlet 
and one with white flowers, and the “ Neari," whose large fruit I sent you 
from Labuan, prevail in muddy places, growing almost or quite in the 
ire ol m imoquaio) «n pstied by Nipa (Nipa fratioane) *Peeai" 
= long stems oe See oaks lor sm Etape quur rena ” 
gellaria ; Dilivaria ilicifolia pom as purpose; I think it is a fi la; 
P T " peces of Pandanus, the “ Kasou 
