230 



A. Carpenter — The Mean Temperature of the 



[No. 2, 



XVI.— Natural History Notes from H. M.'s Indian Marine Survey 

 Steamer 'Investigator,' Commander Alfred Carpenter, R. N., 

 Commanding. No. 8. The Mean Te^nperature of the Deep Waters of 

 the Bay of Bengal. By Commander Carpenter, R. N"., D. S. O., 

 F. R. Met. Soc, F. Z. 8.— Communicated hy The Superintendent op 

 THE Indian Museum. 



[Received August 1st ;— Read August 3rd, 1887.] 

 (With Plate X.) 

 The temperature curves of the deep sea at different points in the 

 Bay of Bengal vary but little at depths greater than 100 fathoms. The 

 larger number of observations have naturally been made in shallow 

 waters, that is to say, in less than 300 fathoms ; but, still, more than one 

 observation has now been obtained for every 100 fathoms down to 1900 

 fathoms. The greatest depth at which the temperature has been ob- 

 tained is 2,105 fathoms, off the east coast of Ceylon, at which depth a 

 Casella-Miller thermometer shewed 33°. 7 Fahr. corrected for pressure, 

 the correction being 0°*8 subtractive. As will be seen by the following 

 example, the uniformity of temperature comes to be a check on the ac- 

 curacy of the thermometers and, vice versa, on the accuracy of the depth 

 found. 



Date. 



No. of 

 Thermo- 

 meter 

 used. 



Depth 

 in Fa- 

 thoms. 



Correct- 

 ed tem- 

 perature. 



Locality. 



3. I. 1885 



29. IV. 1886 



5. V. 1886 



31478 

 19042 

 32096 



675 



675 

 675 



41°-7 

 42'1 

 41-8 



Near the head of the Bay of Bengal. 

 East of Little Andaman Island, 

 Off Colombo, Ceylon. 



Here we see only a variation of half a degree at the same depth in 

 widely different places, and the error of reading off absorbs quite half of 

 that. Unfortunately, the scale is not cut on the thermometer tube but 

 on porcelain at the side ; and, as the bent tube of the Miller- Casella ad- 

 mits of a small movement, care has to be taken to hold the tube firmly 

 against the scale, so that both mercury ends shew similar readings, be- 

 fore taking the reading of the minimum index, which has been pushed 

 up the tube to some lower temperature whilst under water. The uni- 



