44 Temperature of the Ocean. 



fathoms at Station 159, and rose again to 500 fathoms at Station 

 160, so that between Stations 159 and 160, the " Challenger " 

 must have crossed the axis of a current about 500 fathoms deep, 

 and from 500 to 600 miles broad. This current, coming from 

 the Indian Ocean, flows in a south-easterly direction to the 

 southward of Australia, and penetrates into the Antarctic region 

 along the meridian of New Zealand. 



Fig. 7 presents a section, at Station 318, of the great 

 Antarctic current which flows as an under-current along the 

 east coast of South America, crosses the Equator, and pene- 

 trates into the North Atlantic. At the above station it rises to 

 within 100 fathoms of the surface. The steep gradient between 

 the surface and 100 fathoms is due to a branch of the Brazilian 

 current, which flows in a southerly direction towards the Falk- 

 land Islands. 



Curve A, Fig. 8, furnishes a similar example of the presence 

 of a cold stratum at the depth of little more than 100 fathoms 

 from the surface. It is the temperature-curve of Station 147, 

 near the Crozet Islands. Curve B illustrates the case of a cold 

 surface-stratum, probably formed by melting ice, observed in 

 the vicinity of the Antarctic Circle. The temperature falls 

 from — 1°.2 C. at the surface to — i°.y C. at 50 fathoms, but 

 rises to — o°.8 C. at 200 fathoms, o°.o C. at 300 fathoms, and 

 o°.4 C. at a depth of 500 fathoms (Plates 12 and 13), 



Figs. 9 and 10 represent the conditions of temperature near 

 the Equator in the Atlantic and Pacific Oceans. The curve 

 of Fig. 9 belongs to Station 110, near St. Paul Rocks; the 

 curve of Fig. 10 to Station 221, in the basin between Papua 

 and the Caroline Islands. In the former a surface-current, 

 retaining a nearly uniform temperature of 25 C. down to a 

 depth of 30 fathoms, is joined by a steep gradient to an 

 intermediate current which extends from 100 fathoms to 400 

 fathoms, the cold bottom-stratum being reached at a depth of 



