28 INDIAN MARINE SURVEYS. 



sick list, and work was suspended. Places situated on tidal estuaries 

 where fresh, and salt water come into contact are notoriously 

 malarious, and though not of a severe type the disease in this case 

 was extremely persistent. 



The natural history results were meagre during the vear 1886-87, 

 Surgeon G. M. Giles having been deputed to serve with the Chitral 

 and Kafiristan Mission during the greater part of the year. 



Towards the close of March 1887 the " Investigator " completed 

 the survey of the shallows off the mouths of the Meghna river. 

 The soundings on the " South Patches " proved to be even shallower 

 than hitherto supposed. This shoal has caused a great many wrecks 

 from endeavours to avoid it, for sailing vessels arriving off 

 Chittagong with their chronometers often in error after long ocean 

 passages, give it too wide a berth and get wrecked on the Meghna 

 shoals. With the present corrected chart, vessels making for 

 Chittagong should be able to avoid these Patches, while the rectifi- 

 cation of the peaks and outlying islets of the Andaman and Nicobar 

 groups will tend to decrease the wrecks on the flats of the 

 Sundarbans by enabling vessels standing up the Bay of Bengal to 

 fix their true positions. 



From the "South Patches''" a line of soundings was first run 

 south to the latitude of Akyab, and then a line of deep-sea 

 soundings was carried at intervals of 70 miles to Madras, the depths 

 gradually increasing towards the latter place, 1,820 fathoms being 

 obtained -10 miles off Pulicat. near Madras. This line was the first 

 record of the depth of the northern portion of the Bay of Bengal. 



Commander Carpenter's paper on the mean temperature of the 

 Pav of Bengal, with its chart, has been published in the Journal 

 of the Asiatic Society of Bengal for 1887, Vol. LVL, Part II. 

 The temperature records afford an extremely useful check on the 

 observations of depth in cases where the sounding wire indicator 

 gets out of order. 



Off Madias a closely -sounded survey was made, on the scale of 

 two inches to the mile, of the Tripalur reef and Rockingham patch, 

 where three steamers had grounded, one being lost and another 

 very badly damaged. This survey was connected with the land 

 survey stations. A few soundings were also taken north of Pedro 

 Point in Ceylon, where a gap existed in the soundings showing the 

 eastern entrance to Palk straits. 



