58 



The Open Polar Sea. 



is, for about sixty to one hundred miles, a comparatively shallow 

 and gradual slope, when it suddenly dips sharply until the bottom 

 of what is called the telegraphic plateau is reached. This sharp 

 decline leading to the ocean bed is the western boundary of the 

 gulf-stream. Its surface and water boundary is a counter-current oi 

 cold water coming from the east of Greenland and from Davis strait, 

 and one that washes the coast of the United States from Maine to 

 Florida. As the gulf-stream passes Florida it has a maximum surface 

 temperature of eighty degrees Fahrenheit, and a velocity of seventy to 

 one hundred and twenty miles a day. It is here from 2,500 to 3,000 

 feet deep, forty miles wide and exceeds more than a thousand times in 

 volume the Mississippi in its flood.* It gradually lessens its speed and 

 spreads out in width in its northward passage until between New York 

 and the Bermudas the temperature has lowered to seventy degrees and 

 the depth diminished to between 400 and 500 feet. The Azores deflect a 

 portion which bends around the north-west shore of Africa, inclosing 

 the Sargasso sea, the same placid sea filled with ocean weeds and 

 grasses that astonished Columbus and his men as they sailed slowly 

 through it day after day. The main branch of the gulf-stream turns in 

 a north-easterly direction carrying perpetual verdure to Ireland, and 

 on to the north-western coast of Norway, so that garden vegetables 

 may there be expected in their season, often stranding West India 

 fruits on Spitzbergen, and so it moves on to Novaya Zemlya where 

 hitherto it has been lost to human observation. Here knowledge from 

 observation ends, and speculation or logic, if you please, begins. What 

 becomes of it after it reaches the neighborhood of the ice barrier of 

 berg and floe all cemented pell-mell together ? There are two reasons 

 now why the specific gravity of this gulf current is greater than the 

 water fringing the ice barrier. First, the water of the Arctic region 

 has been largely added to from rain and snow, from melted ice from 

 the vast glacier system of Greenland, and, as it is well known, fresh 

 water is lighter than salt. Secondly, water just before it reaches the 

 freezing point loses some of its weight probably by expansion, but lose 

 it, it does in some way. For these reasons the waters of the gulf- 

 stream, as they pass the latitude of Novaya Zemlya, have a greater 

 specific gravity than that bordering the ice barrier, and, consequently, 

 the warmer and heavier current sinks. It dips and passes northward 

 under the ice barrier as an undercurrent. And so it passes on north- 

 wards until it meets a similar current from the opposite side of the 

 globe, or until it has lost its progressive velocity. Having at last given 

 out all its remaining heat to the surrounding polar region, it returns 



