CHAP, v.] GENERAL CONCLUSIONS. 275 



steadily and perceptibly to the bottom, and that the bottom 

 temperature is more than 2° C. lower than the temperature at 

 similar depths in the eastern or the north-western basin. The 

 conditions which exist at the mouth of the trough extend to 

 the equator. 



Figure 54 represents the vertical distribution of temperature 

 at Station CXII., lat. 3° 33' S., long. 32° 16' W., twenty-one 

 miles to the north-west of Fernando Noronha. Figure 55 gives 

 the temperature at Station CXXIX., lat. 20° 12' S., long. 35° 

 19' W., nearly midway between Station CXII. and Station 

 CCCXXYII., one of the most characteristic in the section at 

 present under consideration, represented in Figure 56. The 

 depth at Station CCCXXYII. is 2900 fathoms, and the depths 

 at the two other stations 2150 and 2200 respectively; and it 

 will be seen that at the latter stations the bottom tempera- 

 tures correspond almost precisely with the temperature at Sta- 

 tion CCCXXVII. at like depths. The isothermobath of 2° C. 

 is at the same height, 1500 fathoms, at the two southern sta- 

 tions ; and at the northern station only, near the equator, it 

 sinks to 1800 fathoms. The isothermobaths of 2°-5 and 3° C. 

 correspond within a hundred fathoms or so in level at Stations 

 CXXIX. and CCCXXVII. ; at Station CXII. all the isother- 

 mobathic lines under that of 4° C. down to the line of 1° C. are 

 much lower than at Stations CXXIX. and CCCXXVII. ; that 

 is to say, that at the equator, between 410 fathoms and 2000 

 fathoms, the water is considerably warmer than it is farther 

 south. 



The isothermobath ic lines of 4° and 5° C. seem everywhere 

 in the Atlantic to mark broadly the line of demarkation be- 

 tween the upper zone, where the temperatures are obviously 

 affected by the diffusion of water by wind-currents; and the 

 lower zone, where the temperatures are continuous with those 

 of the Southern Sea. In the Xorth Atlantic they are markedly 

 lower than they are to the south of the equator ; that is to say, 



