NOTES ON DEEP SEA SOUNDINGS. 61 



Captain Thomson was prevented by north-east winds and 

 westerly currents from reaching either the Caroline or Ladrone 

 Islands ; but he reached Nares Harbour in Admiralty Island on 

 the 3rd March, got Soundings on the way, and staid there six 

 days finding the natives friendly : a. good deal of work was done, 

 and Commander Maclear obtained magnetic observations. On 

 the 10th March they were carried westward, out of sight of both 

 the groups mentioned above. On the 23rd March, the Sounding 

 of 4,475 fathoms was reached, in 11° 24' N., and in longitude 

 143° 16' (not as quoted before by me from a private acount in 

 145° 16'.) The distance from New Guinea was about 850 miles. 



In the same spot, and on the same day, as appears by the 

 Abstract of Soundings, appended to Captain Thomson's Report, 

 a Sounding of 4,575 fathoms was obtained, on red clay. On this 

 occasion one thermometer was broken, and on the second two ; 

 the bottom temperature being recordedat 33°*9, and not 35°5 as 

 in the communication I quoted in my Address. 



The difference of the Specific gravities at the surface and at the 

 greatest depth is recorded as between 102585 and 1-02592, the 

 pressure increasing, therefore, under a column of water 27,450 

 feet thick 000007, just one-third of what the proportionate 

 increase was two days before, under a depth of 1,850 fathoms, on 

 Grlobigerina ooze, about 228 miles, a little Westward of North of 

 the position on the 23rd. This is merely a rough deduction of 

 my own, made from the Table of Abstracts. 



In the Sulu Sea the Specific gravity was found, on the contrary, 

 to be higher at the surface than at the bottom, increasing up- 

 wards 0*00025 in 2,225 fathoms water. Commander Tizard 

 says : — " The Specific gravity of the water in the Celebes, Sulu, 

 and Banda Seas was found to be less than in the Pacific Ocean 

 on the surface ; this may be accounted for by the excess of rain- 

 fall over the evaporation in the area occupied by them." The 

 temperatures of the seas just mentioned appear to be nearly con- 

 stant. In the China Sea it is different ; the temperatures vary 

 greatly. This is owing to the fact that nearly one-half of the 

 China Sea is under 100 fathoms in depth. Moreover, the China 

 Sea has in winter a range from 64 degrees at Hongkong to 84 

 degrees at Singapore, whilst the other areas have only slight 

 variations. 



" An examination of the chart of the regions mentioned will 

 show," says Captain Tizard, " that the deep basins of the China 

 and Celebes Seas are alone in communication wdth the Pacific 

 Ocean, and that consequently their temperature must be greatly 

 dependent on the temperature of that part of the Pacific imme- 

 diately adjacent to their opening into that ocean ; for although 

 both seas are in communication indirectly with the Indian Ocean, 

 they are cut off from the deep basin of that ocean by a large tract 



