POLAR CURRENTS. 355 



Bearing these fjxcts in mind, the reader will per- 

 ceive that it is the surface-water only which ever 

 reaches so low a temperature that it is changed to 

 ice ; and he will also perceive that when the wind 

 moves the surface-water, the particles which have be- 

 come chilled by contact with the air mingle in the 

 rolling waves with the warm waters beneath, and 

 hence that ice can only form in sheltered places or 

 where the water of some bay is so shoal and the cur- 

 rent so slack that it becomes chilled to the very bot- 

 tom, or where the air over the sea is uniformly calm. 

 He will remember, however, that the winds blow as 

 fiercely over the Polar Sea as in any other quarter of 

 the world ; and he will, therefore, have no difficulty 

 in comprehending that the Polar ice covers but a 

 small part of the Polar water ; and that it exists only 

 where it is nursed and protected by the land. It 

 clings to the coasts of Siberia, and springing thence 

 across Behring Strait to America, it hugs the Ameri- 

 can shore, fills the narrow channels which drain the 



April 10th, 1865, by W. E. Hickson, Esq., from which I extract the fol- 

 lowing : — 



" It had always been supposed that the immediate areas of the Poles 

 must be the coldest regions of the globe, because the farthest points from 

 the equator. Hence the argument that the higher the latitude the 

 greater must be the difficulties and dangers of navigation. Quite an op- 

 posite opinion, however, had begun to prevail among meteorologists on 

 the publication, in 1817, of the Isothermal system of Alexander Von 

 Humboldt, which showed that distance from the equator is no rule for 

 cold, as the equator is not a parallel of maximum heat. The line of max- 

 imum heat crosses the Greenwich meridian, in Africa, fifteen degrees 

 north of the equator, and rises, to the eastward, five degrees higher, run- 

 ning along the southern edge of the Desert of Sahara. In 1821, Sir 

 Da' id Brewster pointed out, in a paper on the mean temperature of the 

 glal e, the probability of the thermometer being found to range ten degrees 

 higher at the Pole than in some other parts of the Arctic Circle. No new 

 facts have since been discovered to invalidate this conclusion — many, on 

 the contrary, have come to light tending to confirm it." 



