Notices of Books. 
1878.] 
91 
generations become habituated to a gradually freshening 
water. 
It is obvious that Mr. KingsmilPs views can only be thoroughly 
criticised in the deserts and the mountains of Eastern and 
Central Asia, hammer in hand, and there are many points which 
must be more closely examined before his hypothesis can be 
either accepted or rejected. From the point of view of the 
physicist there is, we believe, no preliminary objection to the 
idea of a secular shifting of the earth’s axis of rotation. Sir W. 
Thomson considers it as possible that the poles may have, at one 
or other time, have occupied positions differing from their present 
locality by as much as 40°. Such a variation might place London 
alternately on the Pole and within about io° of the Equator — a 
climatic range fully sufficient to account for the different faunas 
and floras of bye-gone geological epochs. But is there at pre- 
sent any indication that the axis of the earth is shifting its 
position ? If the North Pole is receding from us and approaching 
the eastern parts of Siberia, our longest day ought to be growing 
gradually shorter and our shortest day longer, and the maximum 
apparent altitude of the sun in the heavens ought to be increasing. 
But we are not aware that even any suspicion of such changes 
has been aroused. If, therefore, a secular displacement of the 
earth’s axis of revolution is in progress, it must be exceedingly 
slow — too slow, we think, to have effected any important climatic 
changes in Central and Eastern Asia within the limits of histo- 
rical time. 
Again, for the deterioration which those regions have admit- 
tedly undergone, the author proposes two causes apparently not 
standing in any necessary connection — viz., the displacement of 
the earth’s axis and the elevation of the land in the centre of 
Asia. Is it not possible that the latter cause may alone suffice 
to account for the effedts produced ? A gradual drying up of 
rivers and a paucity of rainfall have also been traced in many 
parts of Central and Southern Europe and of Northern Africa, 
but there has been no distind amelioration of climate beyond 
what is due to improved drainage and other local causes. Yet 
on Mr. Kingsmill’s hypothesis Western Europe and Eastern 
North America ought to be enjoying a progressive elevation of 
their average temperature. 
If the earth’s axis is undergoing secular displacement this 
change will doubtless follow some law, and the poles would 
infallibly describe a regular curve. This curve it will be im- 
portant to trace out as nearly as possible by observing in what 
order of time different parts of the world have undergone glaci- 
ation. Now it is quite possible, supposing Mr. KingsmilPs 
hypothesis to be correct, that Eastern Asia should exhibit no 
marks of a glaciation synchronous with that of Europe and 
North America. But the theory seems to us to require impera- 
tively that Asia should exhibit marks of an earlier glaciation 
