CURRENTS AND WHALING. 507 



we met with but little current until we approached the east coast of 

 Africa. We had, during this part of our voyage, an opportunity of 

 trying the deep-sea temperature daily, having received several self- 

 registering thermometers, which I had sent for to replace those we 

 had lost. These observations confirmed the impression that this 

 portion of the ocean is but little liable to submarine streams. 



On approaching the east coast of Africa, we found ourselves at 

 first influenced, as mentioned in the Narrative, by the Polar Stream, 

 then, as we neared the coast, by the Equatorial Stream that sets down 

 the Mozambique Channel. This stream is usually confined to narrow 

 limits, but at some seasons becomes strong enough to throw its waters 

 in a southwest direction beyond the Aguillas Bank. There is little 

 doubt that this Equatorial Stream is superficial, overlying the Southern 

 Polar Stream, a portion of which latter, touching the Aguillas Bank, 

 is forced up by that obstruction to the surface. This is evident by 

 its reducing the temperature of the waters on soundings at the Cape 

 to 62°. This Polar Stream is divided by the Cape : the eastern part 

 sets along the east coast of Africa as a submarine stream, and on 

 reaching the island of Madagascar is found to flow north, along its 

 west shores. The other and larger portion is deflected, and flows to 

 the northward, along the west coast, and finally forms the Great 

 Equatorial Stream of the South Atlantic. 



We have seen that a great equatorial stream, flowing westward, 

 is found both in the Atlantic and Pacific. One also, according to 

 Horsburgh, exists in the Indian Ocean, in the latitude of 3° N., which 

 may be traced to that polar stream which we have seen to flow along 

 the western coast of New Holland, and which must of necessity 

 sweep the coast of Java and Sumatra. This stream has in the Indian 

 Ocean been observed to flow at the rate of fifty-six miles in twenty- 

 four hours. Upon the same authority, it appears that on the Malabar 

 coast a current sets constantly to the southward. 



About the Chagos Archipelago, the currents are periodic, setting 

 west and northwest during the prevalence of the southeast monsoon, 

 and southeast in the months of December and January, when the 

 wind blows from the northwest. About the Comorro Islands, on the 

 contrary, the prevailing current is from the westward ; and off the 

 north end of Madagascar, likewise, a westerly current prevails 

 throughout the year. On this account the ports of that island are 

 difficult to make, and ought to be approached from the windward, 

 as it would be difficult to beat up to them against the current. 



