NATURAL HISTORY. 



531 



forty or fifty yards in diameter. 

 Now, sucli a number of these 

 pieces collected together in close 

 contact, so that they cannot, fiom 

 the top of the ship's mast, be seen 

 over, are termed a pack. 



When the collection of pieces 

 can be seen across, if it assume a 

 circular or polygonal form, the 

 name of patch is applied ; and it is 

 called a stream when its shape is 

 more of an oblong, how narrow 

 soever it may be, provided the 

 continuity of the pieces is pre- 

 served. 



Pieces of very large dimensions, 

 but smaller than fields, are called 

 floes : thus, a field may be com- 

 pared to a pack, and a doe to a 

 patch, as regards theij' size and ex- 

 ternal form. 



Small pieces which break off, 

 and are separated from the larger 

 masses by the effect of attrition, 

 are called brash-ice^ and may be 

 collected into streams or patches. 

 Ice is said to be loose or open, 

 when the pieces are so far sepa- 

 rated as to allow a ship to sail 

 freely amongst them ; this has 

 likewise been called drift-ice. 



A hummock is a protuberance 

 raised upon any plane of ice above 

 the common level. It is frequent- 

 ly produced by pressure, where 

 one piece is squeezed upon ano- 

 thei", often set upon its edge, and 

 in that |)osition cemented by the 

 frost. Hummocks are likewise 

 formed, by pieces of ice mutually 

 crushing each other, the wreck 

 being coacervated upon one or 

 both of them. To liummocks, 

 the ice is indebted for its variety 

 of fanciful shapes, and its pic- 

 turesque appearance. They occur 

 in great numbers in heavy packs, 

 on the edges and occasionally in 



the middle of fields and floes. 

 They often attain the height of 

 thirty feet or upwards. 



A calf is a portion of ice which 

 has been depressed by the same 

 means as a hummock is elevated. 

 It is kept down by some larger 

 mass J from beneath which, it 

 shews itself on one side. I have 

 seen a calf so deep and broad, that 

 the s'lip sailed over it without 

 touching, when it might be ob- 

 served on both sides of the vessel 

 at the same time ; this, howevei", 

 is attended with considerable 

 danger, and necessity alone war- 

 rants the experiment, as calves 

 have not unfrequently (by a ship's 

 touching them, or disturbing the 

 sea near them) been called from 

 their sub-marine situation to the 

 suiface, and witli such an accele- 

 rated velocity, as to stave th« 

 planks and timbers of the ship, 

 and in some instances, to reduce 

 the vessel to a wreck. 



Any part of the upper superfi- 

 cies of a piece of ice, which comes 

 to be immersed beneath the sur- 

 face of the water, obtains the 

 name of a tongue. 



A bight signifies a bay or sinu- 

 osity, on the border of any large 

 mass or body of ice. It is sup- 

 posed to be called bight fiom the 

 low word bite, to take in, or en- 

 trap ; because, in this situation, 

 shijjs are sometimes so caught by 

 a change of wind, that the ice 

 cannot be cleared on either tack ; 

 and in some case?, a total loss has 

 been the consequence. 



Comparison of Ice frozen from Sea- 

 Water and Rain-Water. 



When the sea freezes, the great- 

 est part of the salt it contains is 

 deposited, and the frozen spangy 



2 M 3 mass 



