1840.] Memoir of Sylhet, Kachar, §• adjacent Districts, 815 



and sand hills of alluvial formation. The coal found at Laour rests on 

 this limestone, which abounds in fossil shells, among which the principal 

 are Terebratula and Producta. The cavern of Booban is situated in this 

 limestone, but no measures have been employed to ascertain if it con- 

 tains any fossil remains. 



The few facts which I am able to add on the geology of the whole 

 country under review, may not improperly find their place here, as they 

 can be of value only when taken collectively to illustrate the general 

 formation. 



In Upper Kachar the dense woods have materially impeded obser- 

 vation, and I can only say, that the table land is there absent, as well as 

 the granite boulders, and that the formation is of primary sandstone, 

 upon which an alluvial formation is posited. No fossil remains have 

 been procured from this quarter. 



The Tippera hills, in the more elevated parts of which we have any 

 knowledge, exhibit primary sandstones underlying an alluvial formation, 

 in which fossil remains are found in sufficient quantity, but no great 

 variety. Those within my own observation have been Madrepires and 

 fossil wood. The alluvial formation over the eastern part of Sylhet 

 and Lower Kachar is of the same nature with that of Tippera, being 

 similar in structure and material. The common feature is a kind of 

 breccia, which is found in masses varying from a mere pebble to enor- 

 mous blocks of many thousand tons weight, and these are imbedded 

 in the clay or sand hills near the surface (never stratified), often m 

 connexion with a thin stratum of a substance exhibiting a highly 

 metallic appearance, and which seems to be oxide of iron. It is impos- 

 sible to examine these black blocks, which on fracture display numer- 

 ous concavities, without entertaining the suspicion of their volcanic 

 origin ; but any doubts on this head must cease on looking at the masses 

 of lava by which they are often accompanied, for that the shapeless 

 lumps to which I allude have been in a state of fusion, admits of no 

 question, being proved by their vitrious lustre, close and brittle texture, 

 and by the presence of blisters formed by the air during the process of 

 cooling. I abstain from noticing the localities of the coal beds, salt 

 wells, and Petroleum spring, as they have been heretofore described. 



It must be acknowledged that our geological knowledge of this quar- 

 ter is still lamentably defective, and that the materials for drawing a 



5 L 



