612 



Dr. W. B. Carpenter on the [June 13, 



Biafra, appears from the fact that (as was first pointed out by Mr. Findlay*) 

 there is a similar counter-current in the Pacific between the Northern and 

 the Southern Equatorial, and that an analogous current is traceable also in 

 the Indian Ocean, setting towards the coast of Sumatra. 



122. With all this evidence of s^r/aee-indraught, therefore, we need 

 have no difficulty in accounting for the constant supply of the " head- 

 water " of the Equatorial Current, without having recourse to the hypo- 

 thesis of a So^om-indraught of Polar water, which is resorted to by Prof. 

 Wyville Thomson (§ 114, in.) to explain the prevalence of a glacial tempe- 

 rature over the Deep-sea bed. It seems obvious, on the axiomatic principle 

 of "least action," that a surface-outfiow will always be replaced by a sur- 

 /^ce-indraught, wherever this can be supplied ; since a bottom-indraught 

 would involve the lifting-up of the whole intervening stratum of water : 

 and I am assured by Mathematicians and Physicists of the highest emi- 

 nence, that this view is not open to question. — We shall hereafter see that 

 the Westerly Drift which answers to the Equatorial Current in the North 

 Atlantic, in its turn draws upon the terminal expansion of the Gulf-stream 

 proper (§ 147). 



123. Passing, now, to the western side of the North and South Atlantic, 

 we observe that in both alike the Isothermal lines bend away from the 

 Equator, in conformity with the known course of the two great divisions 

 of the Equatorial Current. For as this sweeps across from the African to 

 the American side of the Atlantic, and strikes full upon Cape St. Roque, 

 which forms the salient angle of the South American Continent about 5° 

 south of the Equator, it is (as it were) split in two thereby ; and while the 

 larger or northern division is slanted in a N.W. direction towards the Carib- 

 bean Sea, the smaller or southern division is forced to take a decided bend 

 to the southward along the coast of Brazil, forming what is known as the 

 " Brazil Current." This is traceable Southwards, at a gradually diminish- 

 ing rate, as far as the estuary of the Rio de la Plata, in S. Lat. 35°, where 

 it appears to turn to the eastward and to recross the Atlantic, forming 

 what is known as the "Southern Connecting Current/' which enters the 

 South-African Current near its commencement, and thus completes the 

 comparatively simple circulation of the South Atlantic. The Thermal 

 effect of this southward direction of a portion of the Equatorial Current 

 shows itself in a very marked manner in the deflection of the February (or 

 summer) Isotherm of 80° nearly as far south as Rio Janeiro, so as to ap- 

 proach the February Isotherm of 75° within eight degrees on the meridian 

 of 30° W. ; although on the meridian of 20° W. these two Isotherms are 

 twenty-Jive degrees apart. Yet notwithstanding this decided evidence of 

 the thermal power of the Brazil current, its warming influence does not 

 seem to extend itself in any considerable degree beyond the parallel of 

 30° S.; along which we find the February Isotherm of 75° and the August 

 Isotherm of 65° running almost coincidently, until they bend northwards 



* ' Directory for the Pacific Ocean,' vol. ii. pp. 1243-7. 



