44 The Gulf Stream. 



for it is known that on each side of the warm waters of the Gulf 

 Stream there is flowing from the north to the Caribbean Sea a cold 

 current, of equal volume to the stream itself. This, being evi- 

 dently not produced by the trade winds, would seem to refute this 

 theory. 



" Where, then, must we look for the motive power ? Let us 

 suppose a globe of the size of the earth, covered all over with water 

 to a depth of 200 fathoms, from which every source of heat and 

 cause of radiation is removed. Then there would be neither wind 

 nor current. Imagine all the water in the tropics, to a depth of 100 

 fathoms, to become oil. The equilibrium is at once disturbed, and 

 a system of currents commenced, the oil flowing towards the poles, 

 and the water towards the equator. The oil becomes water again 

 at the poles, and the water oil at the equator. Thus, without wind, 

 we should have two continuous currents, similar to what we really 

 see in the earth, one flowing north to the pole, and one to the 

 equator ; and on account of the earth's rotation, the former would 

 have an easterly direction, and the latter a westerly one. If the 

 nucleus of this imaginary globe were then to assume the exact form 

 of the bottom of our seas, and in every respect represent the shoals 

 and islands, the coast lines and continents, this uniform system of 

 currents would be materially altered, but still the general principle 

 would be the same, and the alterations would only make the currents 

 more resemble the Gulf Stream and the Northern Current. The 

 relation between water and oil is the same, in some degree, as 

 between the cold waters of the north and the warm waters of the 

 equator made specifically lighter by the tropical heat." 



This is the theory of Maury. He also attaches great importance 

 to the greater saltness of the water of the Stream than of the Baltic 

 and North Seas. Its waters are heavy, theirs light. *' They are 

 compelled to seek and maintain their level, and so the salt left by 

 the evaporation has to be conveyed away, and mixed up again in 

 due proportion with the Baltic and North Seas. This is done by 

 the Gulf Stream. Now the difference of temperature between the 

 Stream and the ordinary waters of the ocean in winter is twenty or 

 thirty degrees. This may, by expanding the water, compensate 

 for the heaviness caused by the saltness, and leave the waters of 

 the gulf lighter by reason of their warmth. Then, being lighter 

 and cohesive, as it appeared before, they should occupy a higher 

 level than those through which they flow. The middle of the 

 Stream should be two feet higher, according to Maury, than the 

 contiguous waters of the Atlantic. This is proved to be the case. 

 Navigators, drifting along with the Gulf Stream, have lowered boats 

 to try the surface current. The boats would drift right or left, ac- 

 cording as they were east or west of the axis of the Stream, but this 



