THE EARTH. 209 



different parts of the ocean. In general, it is per- 

 ceivable to be heavier, and consequently salter, 

 the nearer we approach the Line.* 



But there is an advantage arising from the salt- 

 ness of the waters of the sea, much greater than 

 what has been yet mentioned ; which is, that their 

 congelation is thus retarded. Some, indeed, have 

 gone so far as to say,t that sea water never 

 freezes ; 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 ac- 

 counts of mariners must have informed us, that 

 at the polar regions it is embarrassed with moun- 

 tains 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, t 

 sometimes diffused into plains of above two hun- 



* Phil. Trans, vol. ii. p. 297. -f- Macrobius. 



f Crantz's History of Greenland, vol. i. p. St. 

 VOL. I. O 



