THE ISLANDS OF THE BAY OF BENGAL. 35 



from 200 to 300 feet elevation, bounding usually fertile valleys of 

 comparatively large size; Some isolated hills, however, may be 

 seeu further iuland, which I estimate to be between 500 and 600 

 feet high. 



" The whole surface appears to be intersected everywhere by 

 numerous steep ravines, which open out in all directions, and cause 

 great difficulty in penetrating to the interior parts of the islands, 

 which, I suppose, lies in general at a very low level. 



" The hills and ridges slope very precipitously along the sides 

 towards the sea, commonly at an angle of about 43° to 45°, and 

 often far more. On their sides, towards the interior, this angle 

 is generally reduced to 20° or 25°, but exceptions can be seen 

 everywhere. 



"The geological formations of the whole of South Andaman 

 and Labyrinth Archipelago, as well as of the southern parts of 

 Middle Andaman, is, as Mr. W. Blandford, of the Greological 

 Survey, informed me, quite indentcal with those of the Arakan 

 coast. 



" A broad strip of an indurated chloritic rock, probably some 

 kind of green stone or trap, pervades the interior from Mangrove 

 Bay and "Watering Cove northwards in the direction of the higher 

 ranges of the eastern coast, and reaches the eastern sea shores at 

 Middle Andaman. The same rocks appear also on Termoklee 

 Island (one of the Labyrinth Islands), where they come in contact 

 with coarsely stratified serpentine rock. This indurated rock 

 appears to be rather felspathic, it is of a greenish color, scarcely 

 stratified, but intersected by veins of quartz and calcareous spar. 

 Small cavities occasionally occur in the rock, exhibiting on the 

 interior of the walls a large number of quartz crystals, and other 

 minerals. It is remarkable that, so far as my observations allow 

 me to judge, this green rock seems to occupy the greater part of 

 the level lands, but it does not form ridges or hills of any height 

 worthy to be noted ; but we know, in fact, nothing about the for- 

 mation of the hills in the interior parts. 



" The next rock, which covers a great area of South Andaman, 

 is a grey sandstone, dipping to south by east with an angle of 

 from 43° to 45,° or thereabouts. This sandstone is throughout of a 

 very fine grain, showing a large proportion of silica, and occa- 

 sionally being rather micaceous. The strata exhibit usually a 

 distinct cubic structure. The rock itself decomposes easily, and 

 forms in general a good clay soil. 



" Along the western coast at Port Mouat this rock is excavated 

 and variously worked out by the sea, exhibiting there many fantas- 

 tically formed rocks, resembling in appearance the limestone 

 rocks on the Mingan Islands. 



" Often, as for instance very finely on Bird Island near Viper, 

 this sandstone is interlaid with thin layers, colored rusty by 

 oxide of iron. 



