THE ARCTIC SEAS. 



45 



ABCTIC NAVIGATION. 



CHAPTER III. 



THE ARCTIC SEAS. 

 Dangers peculiar to the Arctic Sea.— Ice-fields.— Hummocks.— Collision of Ice-fields.— Icebergs.— Their 

 Origin.-Their Size.— The Glaciers which give them Birth.-Their Beauty.-Sometimes useful 

 Auxiliaries to the Mariner.— Dangers of anchoring to a Berg.— A crumbling Berg.— The Ice-blmk. 

 —Fogs.— Transparency of the Atmosphere.— Phenomena of Eeflection and Refraction.— Causes 

 which prevent the Accumulation of Polar Ice.— Tides.— Currents.— Ice a bad Conductor of Heat.— 

 Wise Provisions of ZSTature. 



THE heart of the first navigator, says Horace, must have been shielded with 

 threefold brass— and yet the poet knew but the sunny Mediterranean, with 

 its tepid floods and smiUng shores : how, then, would he have found words to 

 express his astonishment at the intrepid seamen who, to open new vistas to 

 science or new roads to commerce, first ventured to face the unknown terrors 

 of the Arctic main ? 



In every part of the ocean the mariner has to guard against the perils of 

 hidden shoals and sunken cliffs, but the high northern waters are doubly and 

 . trebly dangerous ; for here, besides those rocks which are firmly rooted to the 

 ground, there are others which, freely floating about, threaten to crush his ves- 

 sel to pieces, or to force it along with them in helpless bondage. 



The Arctic navigators have given various names to these movable shoals, 



