VAUT 2.] Mallet: Mud volcanoes of Ramri and Cheduha. 19[ 
the sea, strewn over with worn lumps of coral, and of rock hored by PMadidw^ 
whose shells still remain in the holes. But a large part of the alluvial area on 
the eastern side of the island, not more than a few feet above the sea, does not 
exhibit such evident signs of recent elevation, nor does there appear to be any 
tradition of such large proportion of the island having recently emerged. 
The elevation at the Baranga Islands has been comparatively slight. In one 
place, however, at the north end, I observed oysters sticking to the rock about 
two feet above spring high water mark. Further north again, the effects of the 
great earthquake of 17G2 were of a precisely opposite character, large areas in 
the Chittagong District having been then suhnergedd 
The rocks are of a very similar character throughout the islands, consisting 
almost entirely of shale and sandstone. The former 
Geological character. shades of gray; although sometimes 
well bedded, much more frequently it is clunchy, and not uncommonly passes 
into clay. Almost everywhere it includes numerous large iwegular nodules, or 
short strangulated beds, which are more or less calcareous, and some of which 
are tolerably pirre limestone. These nodules are often traversed by strings of 
calcfspar. Irregular strangulated veins of the same mineral also intersect the 
shales themselves, in places, and the latter are occasionally gypseous, containing 
I small disseminated ciystals of selenite, which, by the weathering away of the 
shales, become scattered about on the surface of the ground. Small nodules of 
clay-ironstone are also met with in this way, but are not very common. Shales 
of the above varieties constitute an important proportion of the entire bulk of 
the rocks. 
The sandstones are usually gray or greenish-gray, more rarely yellowish or 
pure white; sometimes harsh; generally moderately fine-grained, and often 
tolerably hard. Sometimes they are intersected by veins of calcspar, or, like the 
shales, contain irregular nodular calcareous masses. Conglomeritic beds, contain¬ 
ing pebbles from two inches diameter, downwards (which are mainly of white 
quartz), are met with, but rarely, and of trifling thickness. 
Both shales and sandstones not unfrequently contain lignite. It occurs in 
little irregular strings, or in strangulated layers from an inch, or less, up to 
throe or four inches thick, and seldom as much as a foot long. Where these are 
found they generally occur more plentifully in some beds than others, lig-nitiforous 
strata being interbanded with others which contain no carbonaceous matter. 
Woody structure is frequently seen in such layers, which are often merely the 
ends of stems that have been crushed flat. Sometimes the stems are only partly 
converted into lignite, the remainder being silicified, although still black from 
residual carbonaceous matter. In some cases the lignite contains pyrites. Much 
larger stems than the above are occasionally met with, one or two that I saw 
being 18 inches in diameter, and visible for a length of .six or seven feet, but they 
are far from common of such dimensions. 
True seams of coal have also been found—-at Tsetama, in the southern 
part of Ramri, where several outcrops occur, varying from one to six feet thick ; 
1 For this determination I am indebted to Mr. W. Blanford. 
^ .Tonrn. As. Soc., Bengalj XIT, lOiS. 
