INDIAN MARINE SURVEYS. 33 



side of the valley the water appeared to be slightly colder than the 

 normal temperature of those depths. 



Arriving at Port Blair, No. 1 Boat party was landed for the 

 purpose of making a survey of Diligent straits on the one-inch 

 scale, while the "Investigator" visited South Sentinel island and 

 the bank off the S.W. point of Little Andaman, both of which were 

 sounded. 



Before proceeding to the Orissa coast, deep soundings were taken 

 across the bay. The Bay of Bengal proved to have a regular 

 decline towards its mouth, the Andaman and Nicobar ridge forming 

 its eastern boundary (the sea east of the Andamans being a separate 

 basin) ; there is slightly deeper water nearer the coasts than in the 

 centre, and the depth falls very suddenly from the 100 fathom line 

 off the Sunderbunds to the 900-fathom line. If we take the slope 

 of the bed of the bay between the 1,100 and 1,400 fathoms contours 

 as being the true gradient of its fall, unaffected to any great extent 

 by the detritus from the rivers, and carry this gradient, which is 

 only 1 in 396, northward, we find that it brings the bed of the bay 

 up on a level with its surface only when it reaches the foot of the 

 Himalayas. 



The survey of the Orissa coast was begun at the mouth of the 

 Devi river, and first carried to the northward for 24 miles. This 

 survey was on the one-inch scale, and was afterwards carried by 

 the " Investigator " along the coast for a total distance of 199 miles, 

 operations being greatly helped and expedited by the marks erected 

 by the land surveyors. The mouth of the Devi river, the anchorage 

 at Puri, and Gopalpur anchorage were also charted on the four-inch 

 scale. 



During 1889-90. the operations were carried along the Ganjam 

 coast to the south of Gopalpur. A survey of the Coco Islands was 

 also commenced during the same season, as well as an examination 

 of the Bassein River and its approaches, by the boat party under 

 Lieutenant G. S. Gunn, R.N. 



The Report for 1888-89 was the last submitted by Commander 

 Carpenter, R.N., and in it he took the opportunity to draw up a 

 brief review of past work, as well as a forecast of future operations. 

 More than seven years had elapsed since the " Investigator " 

 had made her first surveying trip, and in that time she had run 

 some 44,000 miles, of which just half were actual lines of close 

 soundings taken on various surveys. The " Investigator's " boats 



I Y 2032 i . C 



