THE GULF STREAM. 
45 
where permitted, in the oceapic economy, to, touch the bottom of 
the sea. There is every where a cushion of cool water between 
them and the solid parts of the earth's crust. This arrangement 
is suggestive, and strikingly beautiful. One of the benign offices 
of the Gulf Stream is to convey heat from the Gulf of Mexico, 
where otherwise it would become excessive, and to disperse it in 
regions beyond the Atlantic for the amelioration of the climates 
of the British Islands and of all Western Europe. Now cold wa- 
ter is one of the best non-conductors of heat, and if the warm wa- 
ter of the Gulf Stream was sent across the Atlantic in contact 
with the solid crust of the earth — comparatively a good conductor 
of heat — instead of being sent across, as it is, in contact with a 
cold, non-conducting cushion of cool water to fend it from the 
bottom, all its heat would be lost in the first part of the way,. and 
the soft climates of both France and England would be as that ol 
Labrador, severe in the extreme, and ice-bound. 
57. But to return to the streaks and reservoirs of hot watei' 
below. The hottest water is the lightest ; as it rises to the top, 
it is cooled both by evaporation and exposure, when the surface is 
replenished by fresh supplies of hot water from below. Thus, ii? 
a winter's day, the waters at the surface of the Gulf Stream off 
Cape Hatteras may be at 80°, and at the depth of five hundred 
fathoms — three thousand feet — as actual observations show, the 
thermometer will stand at 57°. Following the stream thence off 
the Capes of Virginia, one hundred and twenty miles, it will be 
found — the water-thermometer having been carefully noted all 
the way — that it now stands a degree or two less at the surface, 
while all below is cooler. In other words, the stratum of water 
at 57°, which was three thousand feet below the surface off Hat- 
teras, has, in a course of one hundred and twenty or one hundred 
and thirty miles in a horizontal direction, ascended, vertically, six 
hundred feet ; that is, this stratum has run up hill with an ascent 
of five or six feet to the mile. 
'58. In the case of boiling springs we perceive how all the as- 
cending water comes up in one column ; that there is no descent 
of surface water through that which is boiling up, but at the side 
of the bubbling. Moreover, in a cold winter's day, the water, as 
it boils up, is relatively warm ; it smokes, grows cool, and the 
surface thermometer will stand highest where it is boiling, lowest 
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