STEJNEGER] ANIMALS AND PLANTS OF NORWAY 501 
Imp. Russk. Geog. Obstch., XLi1, 1906, p. 1510) : “ The depressions 
and elevations need not at all take place uniformly over large areas. 
These processes may occur in entirely different ways in the various 
parts of the same ocean. While one part of the ocean shows great 
depression. or elevation of its floor, another may be affected much 
less, or not at all, or may even show opposite processes. The uneven- 
ness and irregularity of the depressions and elevations may cause 
a very complicated sequence of the physico-geographical as well as 
biological changes.” 
Such diversity does not point to cosmic causes. As a matter of 
fact, the changes of level are so intimately connected ‘with the 
various phases of the glacial phenomena that it seems out of the 
question to regard them as mere coincidences.* 
Of the various theories which have been propounded to account 
for the uneven submergence and elevation of the land masses, the 
one which attributes the depression to the weight of the accumulated 
ice and the elevation to the unloading of the enormous weight by 
melting under different climatic conditions, seems to meet most of 
the requirements which can be put to it. This hypothesis is based 
upon the theory of the elasticity of the earth’s crust, the necessary 
consequence of which is, that if the crust be depressed in some 
places, it must rise correspondingly elsewhere, while between these 
areas there must be a nodal axis, or line, which is practically 
stable, where no motion of any consequence takes place. The 
elasticity of the crust furthermore requires a return movement fol- 
lowing the removal of the depressing agency, a rebound which does 
*The very magnitude of the glacial phenomenon in connection with its 
diversity suggests that it is not due to a single cause but to a concurrence 
of many factors. It may be easy enough to reduce ad absurdum every one 
of the various theories which would account for the whole phenomenon by 
the assumption of a single cause, but it seems possible that a combination 
of the various theories, meteorological, geographical, and astronomical may 
be effected in such a way as to frame a plausible working hypothesis. If 
all the different causes functioned together towards the same end, it would 
not be necessary to work each of them to its extreme, and, therefore, often 
absurd, limit. It might then be unnecessary to move the north pole so very 
far out of its place as would be required if a change of the earth’s axis were 
regarded as the whole solution of the question, nor would it be necessary 
to assume such extreme changes of level as 1,000 to 2,500 sea-meters, if 
the height of the land were alone to account for the fall of temperature. 
Neither would it then be imperative to postulate that an unbroken land bridge 
between Scotland and Greenland absolutely shut off the Arctic Ocean from 
the Atlantic, nor to lower to any very great degree either the temperature or 
the volume cf the Gulf Stream. 
