THE GULF STREAM 



771 



perature, has compelled steamship com- 

 panies to adopt lanes of travel and to 

 make a detour around the region of dan- 

 ger. That the western-bound track was 

 shaving dangerously near the limit of ice 

 in the spring, when bergs are numerous, 

 has been shown, and it is probable that 

 the new lanes now used which lie fur- 

 ther south will be permanently adopted 

 during the ice period. 



THE CAUSE OF OCEAN CURRENTS 



The theories as to the cause of ocean 

 currents have been many. Columbus 

 thought the stars, the air, and the waters 

 of th^ sea all had the same motion 

 around the earth from east to west and 

 declared that the force of the equatorial 

 current had washed away the land and 

 thus formed the Windward Islands. 



Toward the end of the 17th century 

 the belief seemed to be that all ocean cir- 

 culation was maintained by means of 

 subterranean passage or abysses. A cur- 

 rent, upon meeting land, descended into 

 the earth and ran through a tunnel to the 

 other side of the obstruction. 



Strange to say, the writer was called 

 upon in recent years to examine a paper 

 written by a gentleman whose theory 

 was somewhat similar to the above. He 

 believed that all mountain ranges were 

 simply the visible evidence of a tunnel 

 conveying water from one ocean to 

 another, the Rocky Mountain tunnel be- 

 ing the conduit by means of which water 

 was transported from the Arctic to the 

 Gulf of Mexico to form the Gulf Stream. 

 Another theory was that the tropical sun 

 evaporated so much water that the Afri- 

 can Coast current ran to fill up the hol- 

 low so formed. 



In recent times the course of currents 

 has been laid to rivers and the Gulf 

 Stream chiefly to the Mississippi. In act- 

 ual fact about 2,000 such rivers would 

 be required. 



Some eminent men have attributed 

 currents to the revolution of the earth, 

 others to the differences in the density of 

 the ocean at the equator and at the poles. 



Franklin's theory, which has many ad- 

 vocates at the present day, was that the 

 winds produce the current by the air 

 moving over the surface of the water, 



and he illustrated this theory by the fol- 

 lowing: "It is known that a large piece 

 of water, 10 miles broad and generally 

 only 3 feet deep, has by a strong wind 

 had its water driven to one side and sus- 

 tained so as to become 6 feet deep, while 

 the windward side was laid dry." As 

 will be seen later, this is a well-taken ex- 

 ample of the force of the wind in caus- 

 ing the Gulf Stream, but it does not 

 quite show the whole of the truth. 



None of these theories were based 

 upon direct evidence by observations in 

 the Gulf Stream, but all were inferences 

 drawn from temperature of the water, 

 from laboratory experiments, from the 

 drift of vessels, or from reasoning based 

 upon opinions of what ought to be. 



Aluch time and labor has been devoted 

 toward attempting to define the limits of 

 ocean currents and their velocities. Co- 

 lumbus on his first voyage, when nearing 

 his final land fall, was trying to find the 

 depth of the water one day. when he no- 

 ticed that the line inclined to the south- 

 west, from which he concluded that 

 the surface was moving faster than the 

 lower stratum which contained the 

 weight on the end of the line. 



Franklin endeavored to use the ther- 

 mometer to define the limits of the polar 

 and tropical waters, and hence the cur- 

 rent. This method is often correct, for 

 without doubt tropical water is warmer 

 than that coming from the poles, but it 

 has been found that at times the warm 

 tropical water may be blown by the wind 

 over and onto the polar stream and then 

 partake of its motion or, as in the Lab- 

 rador current, underrunning the warm 

 water of the Gulf Stream. Temperature 

 is not a sure indication of how the cur- 

 rent may be setting. 



Almost all governments at one time is- 

 sued instructions to their naval officers 

 and requested the cooperation of the offi- 

 cers of their merchant marine to keep a 

 record of the temperature of the surface 

 water, and by the compilation of these 

 data the supposed limits of most ocean 

 currents were placed upon the charts. 



A method of determining the velocity 

 of the currents has been in use since the 

 introduction of comparatively accurate 

 na^•igation. A vessel is moved at sea, by 



