152 APPENDIX. 



with a velocity nearly in the inverse proportion to 

 its depth under water ; light ice consequently 

 drives faster than heavy ice, and loose ice than 

 fields : loose ice meeting the side of a field in its 

 course, becomes deflected, and its re-action causes 

 a circular motion of the field. Fields may ap- 

 proximate each other from three causes : First, 

 If the lighter ice be to windward, it will, of ne- 

 cessity, be impelled towards the heavier ; second- 

 ly, As the wind frequently commences blowing 

 on the windward side of the ice, and continues se- 

 veral hours before it is felt a few miles distant to 

 leeward, the field begins to drift before the wind 

 can produce any impression on ice, on its oppo- 

 site side; and, thirdly, Which is not an uncom- 

 mon case, by the two fields being impelled towards 

 each other, by winds acting on each from opposite 

 quarters. 



" The closing of heavy ice, encircling a quantity 

 of bay ice, causes it to run together with such 

 force, that it overlaps wherever two sheets meet, 

 until it sometimes attains the thickness of many 

 feet. Drift iee does not often coalesce with such 

 a pressure as to endanger any ship which may 

 happen to be beset in it : when, however, land 

 opposes its drift, or the ship is a great distance 



