of the Day of Bcnjal td'c. 377 



depths with a short outline of the hydrography of the basins 

 themselves. 



Bay of Bengal. — The boundaries of the Bay of Bengal on 

 the north and west are too well known to need mention ; but 

 the exact delimitation of its basin from that of the Andaman 

 Sea has only recently been fixed with exactitude by Com- 

 mander Alfred Carpenter, R.N., D.S.O., in charge of the 

 Indian Marine Survey, to which highly scientific ofiicer I am 

 indebted for much more than the facts alone. 



On looking at a chart of the Bay of Bengal, a chain of 

 islands (the Preparis, Ceros, Andamans, and Nicobars) is seen 

 to extend, with a slight western convexity, from north to 

 south between Cape INegrais in Burraah and Acheen Head in 

 Sumatra. And on referring to Captain Carpenter's Contour 

 Map of the Bay {vide 'Administration Report of the Marine 

 Survey of India for 1888-89 ') all the contour-curves are seen 

 to converge ultimately \^ithin a hundred miles of the western 

 coast of this chain. Quite close to the eastern shore of the 

 chain we find, in the Andaman Sea, depths of from 1100 to 

 1200 fathoms, while in the channels between the islands, 

 which connect the two seas, the depths range from 150 to 

 760 fathoms. This is conclusive proof of the existence of 

 two distinct basins, separated by a comparatively narrow ridge 

 rising into the isolated island peaks of the Andamans and 

 Nicobars. 



The Bay of Bengal thus defined touches in its extremes 

 the meridians betw^een 80° and 94° E. It has a maximum 

 depth at its mouth of nearly 2400 fathoms, and its minimum 

 temperature hitherto recorded (at 2105 fathoms) is 33°" 7 

 Fahr., corrected for pressure (Carpenter, " Mean Temperature 

 of Deep-waters of Bay of Bengal," Journ. As. Soc. Beng. 

 vol. Ivi. pt. ii. no. 2). 



In the northern part, into which the great rivers of India 

 and the eastern ultra-Himalayan region pour their muddy 

 waters, and almost as far south as the 1600 fathom contour, 

 the specimens of the bottom obtained by the ' Investigator ' 

 consist of varying grey, green, blue, and brown muds, wntli 

 comparatively few constituents of direct organic origin ; but 

 in the southern and more open part the ' Investigator ' has 

 almost alv/ays found Glohigerina-ooze {Glohigerina, OrbuUnq, 

 and \a.Yge Pulvinulma). Running through the shoal- water at 

 the extreme northern end, opposite the middle of tlie Brahma- 

 putro-Gangetic Delta, is the Swatch of No-ground. This, 

 which has a direction fairly N.N.E. and S.S.W., is a narrow 

 deep channel of over 300 fathoms in a sea of under 100 

 fathoms, and is reasonably regarded by Captain Carpenter 

 as tiie " scour " of the rivers. 



