32 THE PHYSICAL GEOGRAPHY OF THE SEA. 



and that every source of heat and cause of radiation be removed, 

 so that its fluid temperature becomes constant and uniform through- 

 out. On such a globe, the equilibrium remaining undisturbed, 

 there would be neither vv^ind nor current. 



20. Let us now suppose that all the water within the tropics, 

 to the depth of one hundred fathoms, suddenly becomes oil. The 

 aqueous equilibrium of the planet is thereby disturbed, and a gen- 

 eral system of currents and counter currents is immediately com- 

 menced — the oil, in an unbroken sheet on the surface, running to- 

 ward the poles, and the water, in an under current, toward the 

 equator. The oil is supposed, as it reaches the polar basin, to be 

 reconverted into water, and the water to become oil as it crosses 

 Cancer and Capricorn, rising to the surface and returning as before. 



21. Thus, without windy we should have a perpetual and uni- 

 form system of tropical and polar currents. In consequence of 

 diurnal rotation of the planet on its axis, each particle of oil, were 

 resistance small, would approach the poles on a spiral turning to 

 the east, with a relative velocity greater and greater, until, finally, 

 it would reach the pole and whirl about it at the rate of nearly a 

 thousand miles the hour. Becoming water and losing its velocity, 

 it would approach the tropics by a similar, but inverted spiral, 

 turning toward the west. Owing to the principle here alluded to. 

 all currents from the equator to the poles should have an eastward 

 tendency, and all from the poles toward the equator a westward. 



22. Let us now suppose the solid nucleus of this hypothetical 

 globe to assume the exact form and shape of the bottom of our 

 seas, and in all respects, as to figure and size, to represent the 

 shoals and islands of the sea, as w^ell as the coast lines and con- 

 tinents of the earth. The uniform system of currents just de- 

 scribed would now be interrupted by obstructions and local causes 

 of various kinds, such as unequal depth of water, contour of shore- 

 lines, &c. ; and we should have at certain places currents greater 

 in volume and velocity than at others. But still there would be 

 a system of currents and counter currents to and from either pole 

 and the equator. Now do not the cold waters of the north, and 

 the warm waters of the Gulf, made specifically lighter by tropical 

 heat, which we see actually preserving such a system of counter 

 currents, hold, at least in some degree, the relation of the sup- 

 posed water and oil ? 



