jtfj A HISTORY OF 



general, it is perceivable to be heavier, and consequently salter, ths 

 oearer we approach the line.* 



But ihere is an advantage arising from the saltness of the waters of 

 the sea, much greater than what has been yet mentioned ; which is, 

 that thuir congelation is thus retarded. Some, indeed, have gone so 

 far as to say, that sea-water never freezes :t but this is an assertion 

 contradicted by experience. However, it is certain that it requires a 

 much greater degree of cold to freeze it than fresh-water ; so that, 

 while rivers and springs are seen converted into one solid body of 

 ice, the sea is always fit for navigation, and no way affected by the 

 coldness of the severest winter. It is, therefore, one of the greatest 

 bLessings we derive from this element, that, when at land all the stores 

 of nature are locked up from us, we find the sea ever open to our 

 necessities, and patient of the hand of industry. 



But it must not be supposed, because in our temperate climate we 

 never see the sea frozen, that it is in the same manner open in every 

 part of it. A very little acquaintance with the accounts of mariners, 

 must have informed us, that at the polar regions it is embarrassed with 

 mountains and moving sheets of ice, that often render it impassable. 

 These tremendous floats are of different magnitudes ; sometimes 

 rising more than a thousand feet above the surface of the water :| 

 sometimes diffused mto plains of above two hundred leagues in length ; 

 and, in many parts, sixty or eighty broad. They are usually divided 

 by fissures ; one piece following another so close, that a person may 

 step from one to the other. Sometimes mountains are seen rising 

 amidst these plains, and presenting the appearance of a variegated land 

 scape, with hills and valleys, houses, churches, and towers. These 

 are appearances in which all naturalists are agreed ; but the great 

 contest is respecting their formation. Mr. Buffon asserts,^, that they 

 are formed from fresh-water alone, which congealing at the mouths 

 of great rivers, accumulate those huge masses that disturb navigation. 

 However, this great naturalist seems not to have been aware that there 

 are two sorts of ice floating in these seas ; the flat ice, and the moun 

 tain ice : the one formed of sea-water only ; the other of fresh.|| 



The flat or driving ice, is entirely composed of sea-water ; which, 

 upon dissolution, is found to be salt ; and is readily distinguished 

 from the mountain, or fresh-water ice, by its whiteness, and want of 

 transparency. This ice is much more terrible to mariners than that 

 which rises up in lumps : a ship can avoid the one, as it is seen at a 

 distance; but it often gels in among the other, which, sometimes 

 closing, crushes it to pieces. This, which manifestly has a different 

 origin from the fresh-water ice, may perhaps have been produced in 

 the Icy Sea, beneath the pole ; or along the coasts of Spitzbergen or 

 Nova Zembla. 



The mountain ice, as was said, is different in every respect, being 

 formed of fresh-water, and appearing hard and transparent ; it is 

 generally of a pale green colour, though some pieces are of a beauti- 

 ful sky-blue ; many large masses also appear gray, and some black 



Phil Trans, vol. ii. 



p. 297. f Macrobius. f Crantz's History of Greenland- voL i p. 3\ 

 Buffon, vol. ii. p. 91. || Crantz. 



