THE GEEAT EQUATOEIAL CUERENT. 81 



Widening more and more on the side of tlie open sea, Humboldt's 

 current ends by abandoning the coast-line, and bending towards the 

 west, to mix its waters with those of the equatorial current tending 

 from east to west across the Pacific. This liquid moving mass is un- 

 doubtedly the most powerful oceanic river of our planet. According 

 to Daperrey, it has a mean width of no less than 3500 miles, from 

 the twenty-sixth degree of south latitude to the twenty-fourth degree 

 of north latitude, and on its immense journey in a straight line 

 round the world, it traverses from 130 to 140 degrees of longitude ; 

 that is to say, more than a third of the circumference of the globe. 

 Its average speed is like that of Humboldt's current^ about 19 miles 

 per day, but in certain places according to the seasons an advance 

 twice as rapid has been ascertained. What the quantity of this 

 enormous mass of water can be that is thus displaced from one end 

 of the sea to the other, is unknown ; for it would be first necessary 

 to know the mean depth of the current, but this the sounding-lead 

 has not yet discovered. It is only known that at the point where 

 the water from the pole turns towards the west, to enter the great 

 equatorial stream, it proceeds " en masse " in one direction, with a 

 depth of not less than a mile. 



In the midst of the innumerable islands which are scattered over 

 the Pacific, the general regularity of the great current is frequently 

 disturbed, at least on the surface, in consequence of evaporation, 

 rains, and even by the incessant labours of the coral-building 

 zoophytes, which in various ways disturb the equilibrium of the ocean. 

 But under the threefold influence of the terrestrial rotation, the trada- 

 winds, and the great tidal wave which is propagated from east to west 

 across the ocean,* the quantit}^ of water moved each day towards the 

 west is certainly several tens of thousands of cubic miles. The only 

 anomaly in this prodigious movement of the waters of the Pacific 

 which seems inexplicable is the existence of an oceanic river flowing 

 in an opposite direction to the principal current. This reflux has 

 been observed to the north of the equator over a mean breadth of 

 upwards of 300 miles ; elsewhere its speed is variable, and its ad- 

 vance is not always in the direction of due east. In the absence 

 of measurements and positive experiments which permit us to give 

 an exact account of the progress of this counter-current in the dif- 

 ferent seasons, several hypotheses have been suggested to exjolain 

 its origin. The common opinion is that it is masses of water turned 

 aside on their course and thrown back by submarine plateaux, f 



* See below, p. 101. f Ilerschel, Tlnjmal Geography. 



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