Searles V. Wood, Jan, — The Climate Controversy, 445 



while to pursue the subject further into details ; because, if we 

 grant the largest concessions to this theory, two apparently insuper- 

 able difficulties seem to me to present themselves to it as an expla- 

 nation of the Glacial Period proper. One is that the probabilities are 

 enormous against these changes having simultaneously taken place to 

 an exactly similar degree in both hemispheres, so as to produce an 

 apparently equal increase of glaciation, or, to be more accurate (as 

 we do not know the immediate pre-glacial geology of the southern 

 hemisphere), against their having simultaneously passed away to a 

 similar degree in both; and the other is the difficulty to which reference 

 has been already made in considering cause No. 3, viz. the existence 

 of the same differences between the limits of glaciation in Europe 

 and eastern North America, during the Glacial Period, as prevail 

 between corresponding latitudes in those countries in respect of 

 winter cold at the present day. 



It may be worth while, however, before leaving the subject of 

 No. 4, to notice that, in reference to the higher temperature of the 

 Miocene climate, we seem to find that presence of equatorial land 

 which the theory of Sir Charles Lyell would demand as its cause, 

 in the wide stretch of continent which we have every reason to 

 believe extended at that time through the Indian Ocean, and which 

 we may suppose formed about that period the place of man's origin ; 

 and round the sunken site of which the lowest existing races of 

 man are now found grouped. 



No. 5. — The cause suggested under this head, a change in the 

 earth's axis, was naturally the first which would occur to geologists 

 on discovering, as they did almost at the outset of their science, the 

 evidences of a warmer climate having in past ages prevailed in 

 those countries where their investigations were originally pursued. 

 The concurrence of opinion among astronomers, however, that if any 

 change had taken place in the axis of rotation, traces of it would have 

 been left which they could detect, but did not, induced this theory to 

 be generally rejected. It was, however, revived some few years ago by 

 Mr. John Evans, in a memoir read before the Eoyal Society, and has 

 been again touched upon by him in his late Presidential Address 

 to the Geological Society of London. In his memoir Mr. Evans, 

 in order to meet the objections raised by astronomers to any altera- 

 tion in the axis of rotation, suggested that the exterior shell of the 

 earth might be comparatively so thin that, resting on a fluid nucleus, 

 it slided over it ; so that all parts of the surface might undergo 

 changes in relation to this axis, without the j^osition of the axis 

 relatively to the spheroid as a whole being changed. In his late 

 Address, however, he discusses the possibility of a change of axis on 

 different grounds, quoting the opinion of the late Sir J. W. Lubbock, 

 that if from any cause the axis of rotation did not coincide with the 

 axis of figure, the pole of the axis of rotation would describe a sjoiral 

 round the pole of the axis of figure until it became identical with 

 it. He then adverts to the great depth which the late deep-sea 

 investigations have disclosed, as stretching over a great portion of 

 the equatorial oceans, and suggests that these show that the equa- 



