POLAR-ICE. — rUOrEllTIES OF FIELDS. 247 



The occasional rapid motion of fields, with the 

 strange effects produced by such immense bodies 

 on any opposing substance, is one of the most 

 striking objects the polar seas present, and is cer- 

 tainly the most terrific. They not unfrequent- 

 ly acquire a rotatory movement, whereby their cir- 

 cumference attains a velocity of several miles 'per 

 hour. A field thus in motion, coming in con- 

 tact with another at rest, or more especially with 

 another having a contrary direction of movement, 

 produces a dreadful shock. A body of more than 

 ten thousand millions of tons in weight *, meeting 

 with resistance, when in motion, produces conse- 

 quences which it is scarcely possible to conceive ! 

 The weaker field is crushed with an awful noise ; 

 sometimes the destruction is mutual : pieces of huge 

 dimensions and weight, are not unfrequently piled 

 upon the top, to the height of twenty or thirty feet, 

 while a proportionate quantity is depressed be- 

 neath. The view of those stupendous effects in 

 safety, exhibits a picture sublimely grand ; but 

 where there is danger of being overwhelmed, ter- 



• A field of thirty nautical miles square, and thirteen feet 

 in thickness, would weigh somewhat more than is here men- 

 tioned. Allowing it to displace the water in which it floats, to 

 the depth of eleven feet, the weight would appear to be 

 10,182,857,142 tons nearly, in the proportion of a cubic foot 

 of sea-water, to 64 lb. 



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