184 BROWN & HERON: GEOLOGY AND ORE DEPOSITS OF TAVOY. 



and streaks of ferruginous and clayey material. The exposures 

 are completely surrounded by thick recent deposits of river sand 

 and gravel, so that it is impossible to say definitely that they belong 

 to the Mcrguis, though it is probable. Other occurrences, however, 

 have been stated by Mr. Sethu Rama Rau and Mr. Vinayak Rao 

 to be interbedded with the Merguis. 



It is probable that the limestone appears more in streams than 

 on land, because it is easily acted on by the humic acids from the 

 abundant vegetation, and so below a soil covering is rapidly 

 dissolved and removed, while it is comparatively resistant to the 

 mechanical erosion of the river and the feebler solvent effect of the 

 purer river water. 



Certain limestone occurrences at a height of 1,500 to 2,000 feet 

 above the Great Tenasserim, and also that uncovered in the Kanbauk 

 alluvial workings and near Pagaye, may belong to the Moulmein 

 limestone, so prominent in the Amherst and Mergui districts to the 

 north and south, but this is doubtful. 



Granite and Pegmatite. 



The area over which granite appears at the surface is little 

 . inferior in extent to that occupied by the 



Mergui Series, and there is little doubt that 

 the various intrusions, with the exception of the tourmaline pegma- 

 tites, are from the same magma, are of the same age and are con- 

 tinuous underground. 



All the major granite bodies are markedly elongated parallel 

 to the general strike, i.e., about north-north-west-south-south-east, 

 and have most of their lobes extending in the same direction. 



The intrusions fall naturally into six groups : — 



(a) the Moscos Islands, 



(b) the Coastal Range, 



(c) the Frontier Range, 



.,. ., n , , . C Sinbo-Sinma, 



(a) the Central intrusion < „ , t, . _, , 



^ Central Range proper and Paungdaw, 



(e) the Mintha intrusion, 



(/) the Amya intrusion. 



(a) The Moscos Islands. — These islands lie parallel to the Tavoy 



coast, at a distance of fifteen to twenty miles off, from near the 



entrance to the Heinze Basin to south of Launglon. They have 



not been visited by a member of the party, but as seen from the 



