Ice | 53 
a dull leaden color and all wind ripples disappear. Snow fall- 
ing into freezing water forms snow slush. It may be distin- 
guished from ordinary slush by the crystal shapes. If the 
water is calm ice rind will form, a thin sheet less than two 
inches in thickness. A ship makes no noise passing through 
slush, but makes a distinctive sound passing through rind. 
MORE KINDS OF SEA ICE 
If there are winds and waves an ice rind cannot form, but 
the slush may be compacted into lumps called sludge ice. 
Sometimes these lumps take on a circular disklike shape with 
raised edges, and then are known as pancake ice. If sludge 
ice is compressed further into a thick layer it is called slob 
ice and is an effective barrier against small vessels. Newly 
frozen stretches of ice from two to eight inches thick are 
known as young ice, a strong resilient layer, not easily broken 
by swells, greenish in color, and moist on top. As the young 
ice grows it reaches a thickness of one to three feet, and then 
is known as level ice. Level ice often remains a whole winter 
intact when in sheltered places, but is soon broken to pieces 
in the open sea. As it is jammed together it builds up piles of 
broken pieces, heaped one atop another in a haphazard man- 
ner, forming long ridges and grotesque mounds known as 
hummocky ice. All of this ice is broken up in the course of 
time. The fragments are classified as follows: 
Large tabular masses 1/10 to 1/2 mile across: floes 
Tabular masses 10 yds. to 1/10 mile across: small floes, 
cake ice 
Smaller fragments: cake ice 
Irregular masses, 3 to 7 ft. above water: growlers 
Less than two feet above water: bits, or in large numbers 
sometimes called brash ice. 
