THE GULF STREAM. 45 



where permitted, in the oceanic economy, to touch the bottom of 

 the sea. There is every where a cushion of cool water between 

 them and the sohd parts of the earth's crust. This arrangement 

 is suggestive, and strikingly beautiful. One of the benign oiBces 

 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 amehoration 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 Vv^ater 

 below. The hottest water is the hghtest ; 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 w^ater 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 



