METEOROLOGY. 317 



thermonietric colnmn will, during the month of May, rise faster at 

 Quebec than in Florida, and still more rapidly at the Arctic Circle. 

 It was proved, in Section IV, that the Sun's intensity upon the 

 Pole during eighty-five days in summer, is greater than upon the 

 Equator. Indeed, at the summer solstice it rises to 98.6 thermal 

 units, corresponding nearly to 98° Fahrenheit, which singularly 

 coincides with the temperature of the human body, or blood heat. 

 Though this circumstance may invest the Hyperborean region with 

 new interest, still we cannot assume a brief tropical summer with 

 teeming forms of vegetable and animal life in the centre of the frozen 

 zone. For the measured intensity refers to the outer limit of the 

 atmosphere, upon which the sun shines continually, but from a low 

 altitude which cannot exceed 23° 28'. Much of the heat must, there- 

 fore, be absorbed by the air, as happens near the hours of sunrise 

 and sunset in our climate. Also " the vast beds of snow and fields of 

 ice, which cover the land and the sea in those dreary regions, absorb, 

 in the act of thawing or passing to the liquid form, all the surplus 

 heat collected during the continuance of a nightless summer. But 

 the rigor of winter, when darkness resumes her tedious reign, is like- 

 wise mitigated by the warmth evolved as congelation spreads over 

 the watery surface." {Encyc. Brit., article Climate.) 



The sun's intensity may yet have a somewhat greater effect upon the 

 pole where it pierces a thinner stratum, of the atmosphere than over 

 another portion of the earth's surface. For, in consequence of the 

 centrifugal force of the earth's diurnal motion, the particles of air in 

 all other parts of the earth, being thrown outwards, tend to an in- 

 creased thickness in spheroidal strata. We might thence infer that a 

 less proportion of the sun's rays would be absorbed, and a greater 

 portion transmitted through the atmosphere to the siirface of the 

 earth. However this may bp in the immediate vicinity of the Pole, 

 yet in the high latitudes hitherto visited by navigators, and which 

 are not nearer than about five or six hundred miles from the North 

 Pole, according to Dr. Kane and others, a dense and lasting fog 

 prevails after the middle of June, through the rest of the summer 

 season, and effectually prevents the rise of temperature which the 

 sun's intensity would otherwise produce. 



"The general obscurity of the atmosphere arising from clouds or 

 fogs is such, that the sun is frequently invisible during several suc- 

 cessive days. At such times, when the sun is near the northern 

 tropic, there is scarcely any sensible quantity of light from noon to 

 midnight." {Scoreshy's Arctic Regions, Vol. I, p. 378.) ''The 

 hoar-trost settles profusely in fantastic clusters on every prominence. 

 The whole surface of the sea steams like a lime-kiln, an appearance 

 called the frost smoke, caused, as in other instances of the production 

 of vapors, by the waters being still relatively warmer than the in- 

 cumbent air. At length the dispersion of the mist, and the conse- 

 quent clearness of the atmosphere, announce that the upper stratum 

 of the sea itself has become cooled to the same standard ; a sheet of 

 ice quickly spreads, and often gains the thickness of an inch in a 

 single night." 



The question of an open unfrozen sea in the vicinity of the North 

 Pole has long been agitated. In this connection we shall only glance 



