Other observations also amply sustain the conclusions
of Helland. As already stated, the Danish surveying party
under Steenstrup, after several years' work upon the south-
western coast of Greenland, have ascertained that the nu-
merous glaciers coming down to the sea in that region and
furnishing the icebergs incessantly floating down Baffin's
Bay, move at a rate of from thirty to fifty feet per day,
while Lieutenants Ryder and Bloch, of the Danish Navy,
who spent the year 1887 in exploring the coast in the
vicinity of TJpernavik, about latitude 73°, found that the
great glacier entering the fiord east of the village had a
velocity of ninety-nine feet per day during the month of
August.*

It is easier to establish the fact of glacial motion than
to explain how the motion takes place, for ice seems to be
as brittle as glass. This, however, is true of it only when
compelled suddenly to change its form. When subjected
to slow and long-continued pressure it gradually yet readi-
ly yields, and takes on new forms. From this capacity of
ice, it has come to be regarded by some as a really viscous
substance, like tar or cooling lava, and upon that theory
Professor Forbes endeavours to explain all glacial move-
ment.
The theory, however, seems to be contradicted by fa-
miliar facts ; for the iceman, after sawing a shallow groove
across a piece of ice, can then split it as easily as he woulu
a piece of sandstone or wood. On the glaciers themselves,
likewise, the existence of innumerable crevasses would
seem to contradict the plastic theory of glacier motion ;

* Nature, December 29, 1887.
