34 PHILOSOPHICAL SOCIETY OF WASHINGTON. 
large areas of depression and without motion as a whole, but when 
sufficiently accumulated overflowing the edges of its basin in various 
directions; as valley-ice, filling wide valleys of gentle incline both 
as to their axes and their lateral slopes, producing masses of ice 
moving in a definite direction but without lateral and sometimes 
even without terminal moraines; as ice-cascades, formed in sharp nar- 
row ravines of very steep inclination, usually without well-defined 
surface moraines; as typical glaciers, showing névé and lateral and 
terminal moraines; and lastly, as effete or fossil glaciers, whose 
sources have become exhausted, whose motion has therefore ceased, 
and whose lower portions have become smothered by the accumu- 
lation of non-conducting débris. The very existence of one of these 
last has remained unknown for half a century, though the plateau 
underwhich it is buried has been described and mapped by explorers. 
Another form under which ice appears in Alaska is that of solid 
motionless layers, sometimes of great thickness, interstratified with 
sand, clay, etc. A deposit probably of this character is described 
by Nordenskiéld, on the Asiatic coast, near Bering Strait. In 
Alaska this formation, in which ice plays the part of a stratified 
rock, extends from Kotzebue sound, where the greatest known 
thickness of the ice-layer, about three hundred feet, has been noted, 
around the Arctic coast, probably to the eastern boundary.- In 
Kotzebue Sound the ice is surmounted by about forty feet of clay 
containing the remains of fossil horses, buffaloes (Bos latifrons, etc.), 
mountain sheep, and other mammals.. Farther north the ice is 
covered with a much thinner coat of mineral matter or soil, usually 
not exceeding two or.three feet in thickness, and rarely rises more 
than twelve or fifteen feet above high water mark on the sea coast. 
Its continuity is broken between Kotzebue Sound and Icy Cape by 
rocky hills composed chiefly of carboniferous limestones, which 
bear no glaciers and do not seem to have been glaciated. The 
absence of bowlders and erratics over all this area has. been noted 
by Franklin, Beechey, and all others who have explored it. The 
remarkable extent and character of the formation was unknown 
previous to the speaker’s investigations, though the“ice cliffs of 
Kotzebue Sound had attracted attention from the time of their first 
discovery. 
Mr. Datu desired especially to emphasize the distinction between 
these strata of pure ice and the “frozen soil” so often alluded to 
by arctic explorers. The absence of frozen soil in the alluvium 
