8 GREENLAND OR POLAR ICE. 



upon the fields. They have been repeatedly met 

 with, not only upon these continuous sheets of 

 ice, but on the ice of close packs, to the utmost 

 extent to which ships have penetrated. 



On the tremendous Concussions of Fields. 



The occasional rapid motion of fields, with the 

 strange effects produced on any opposing substance, 

 exhibited by such immense bodies, is one of the 

 most striking objects this country presents, and is 

 certainly 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 

 a contrary direction of movement, produces a 

 dreadful shock. A body of more than ten thou- 

 sand millions of tons in weight*, meeting v/ith re- 

 sistence, when in motion, the consequences may 

 possibly be conceived '. The weaker field is crush- 

 ed with an awful noise ; sometimes the destruc- 



* A field of thirty nautical miles square surface, 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>857jl42 nearly, in the proportion oi a cubic foot of 

 sea-water, to 64]b» 



