SEKIAL TEMrERATURES. 21 



than south off Callao. Off the former locality the curves of 38', 40', 50', and 

 60° are near the coast at 850, 650, 250, and 30 fathoms. Off Callao they 

 are at 700, 550, 150, and 40 fathoms. That is, the cold water extends from 

 150 to 100 fathoms nearer the surface off Callao than at Aguja Point. 



In the line from Callao to Easter Island (PI. 10, fig. l) we begin near 

 the coast at Station 4509* with a surface temperature of 67'; between this 

 station and Station 4676, the surface temperature varies rapidly, passing 

 to 65° then 70° and 69° at the last station. At Station 4681 it has risen 

 to 70°, again rising further west to 70°.6^ 72°, 73°, 74°, at Stations 4683, 

 4685, 4687, 4689, 4691, dropping to 73° and 71° near Sala y Gomez and 

 between it and Easter Island, when it rises again to 74° ^ at Stations 4512*, 

 4693, 4513*. 



At the stations which are nearly on the 20' S. Lat. (PI. 11), the 

 surface temperature of 70.6 at Station 4683 gradually increases as we 

 go west to 73°, 75', 81°.5, and 81° at Stations 4685, 4699, 4737, and 4532 *. 



The rapidity with which the temperature of the Humboldt current drops 

 from the surface to a very moderate depth is shown in Plates 4, fig. 2 ; 6, 

 fig. 2; 10, fig. s. At Station 4713, south of the Galapagos, the temperature 

 at 15 fathoms is about the same as at the surface — 75°.2. It has fallen 1° 

 at 30 fathoms, it has dropped nearly 12° at 50 fathoms, and 6° more at 75 

 fathoms, and has fallen to 54°. 9 at 100 fathoms, a difference in 100 fathoms 

 of 20°.3. 



At Station 4651 off Aguja Point near the coast, about in the same 

 latitude as that of Station 4713, the surface temperature of 67° has only 

 dropped to 57°.5 at the depth of 100 fathoms, the body of water between 

 the surface and 75 fathoms being colder. 



At Station 4683 on 20° S. Lat., at a greater distance from land, the 

 surface temperature is 70°.6, and at 125 fathoms is still over 62° (62°. 5), the 

 water off the western edge of the Humboldt current being much warmer to 

 a depth of 125 fathoms than that in the Humboldt current itself. 



At Station 4685, a little more to the south and west than Station 4683, 

 the body of water down to 200 fathoms is as a whole warmer than at the 

 stations to the eastward. 



Taking a section in a northwesterly direction from Callao (PI. 8), we note 

 the same increase of surface temperature as we go west. 



At Station 4670, on the western edge of Milne-Edwards Deep, the tem- 



^ A current runs north to south bctwoen Sala y Gome/, and Easter Island. 



