232 Notes on the Geology of the Vicinity of Port Blair. [No. 3, 



full discussion of this question, reference must be made to Dr. 

 Hochstetter's paper and Dr. Stoliczka's note* on the 

 age of the Andaman sandstone rocks. 



For convenience of reference, I have arranged my field observa- 

 tions and deductions from them under the headings of a few of the 

 principal localities commencing with — 



Eoss Island. — The geology of Eoss Island, the head quarters 

 of the Port Blair settlement, is particularly simple. The rocks are 

 fine bluish grey sandstones with interbedded layers of argillaceous 

 shales (mud-stones). The strike of the beds is almost uniform 

 throughout the island being from N. 15° E. to S. 15° W. ; in no 

 case does it vary more than 5° on either side of that bearing. The 

 dip is high, in some places being 60° ; but 55° to W. 15° N. which 

 is the amount of the inclination of the face of bare rock exposed on 

 the west of the island underneath the barrack buildings may be 

 taken as the fair average amount. On the east and south-east, I 

 observed dips as low as 30°, 28°, 25°, but these are evidently due to 

 local subsidence. At the south end of the island, where the beds 

 are seen distinctly striking across the channel to South point and 

 Cohbyne's Cove, the dip is 55°, and in one bed 60°. 



The above stratigraphical conditions which are roughly repre- 

 sented in the accompanying sketch section of the island arc suebj 

 it will be observed, as are eminently conducive to landslips ; not 



Seciicn CLcrcss^Rs-ss Islcuid' ' aJ,t)ie Norih end 

 ScaJy 1 Inch = 5C Yards. 





* Verhandlungeu der geol. Rcichs-Anstalt, Wien 3 No. 9, 1868. 



