SIN CIDVIAS, JRO SI GHOVEIN INS 79 
Sea water freezes at a temperature of.about 28° Fahr. With 
respect to temperature, sea water ice is believed to behave like 
otnemices Although ice never (covers theysea irom shore to 
shore, except in narrow bays, fjords, etc., belts of ice of consid- 
erable width are formed on its surface in high latitudes. This 
ice is sometimes broken up during the violent storms of winter, 
and uniformly suffers this fate in the storms of spring. Thus 
arise blocks or “pans” 
acres in extent. These blocks of floating ice, frozen together in 
of floating ice, some of which are many 
larger or smaller numbers, constitute the ice-floe of the northern 
seas. The ice of the sea is subject to all the movements which 
affect the ice of lakes, and to such additional movements as the 
tides may bring about. Since the waves of the sea are stronger 
than the waves of lakes, the ice of the sea may be correspond- 
ingly more effective in wearing its shores. 
The striae produced at any given period by pan-ice or ice- 
floe, must be confined to the shores. As developed at any one 
period of time, their vertical range must be exceedingly small, 
and the altitude at which they occur should nearly correspond at 
all points about the margin of any body of water on the shores 
of which they are formed. A great vertical range might con- 
ceivably be given to shore-ice or pan-ice striz, if the water level 
was inconstant in relation to the land. If the land along shore 
were to rise gradually a thousand feet, or if the sea were to fall an 
equal amount, it can be conceived that shore-ice might produce 
strie throughout the whole vertical range between the first and last 
water levels, if all conditions were favorable. But even on the 
most liberal interpretation possible, this conception does not at 
all meet the case of the striz which are associated with our drift. 
Not to speak of other difficulties, the systematic arrangement of 
these striz (see Vol. II., p. 849) is altogether fatal to the idea 
that ice along any shore, or along any combination of shores, was 
the principal agent concerned in their production. 
If it be conceived that the whole area of land covered by drift 
was beneath the sea during the drift period, every part of the 
land surface, as it emerged, must at some time have been a sea 
