504 



ISLAND LIFE. 



[part II. 



and that the radically different distribution of land and sea in 

 the northern and southern hemispheres has generally led to 

 great diversity of climate in the Arctic and Antarctic regions. 

 The form and arrangement of the continents is shown to be 

 such as to favour the transfer of warm oceanic currents to the 

 north far in excess of those which move towards the south, and 

 whenever these currents had free passage through the northern 

 land-masses to the polar area, a mild climate must have pre- 

 vailed over the whole northern hemisphere. It is only in very 

 recent times that the great northern continents have become 

 so completely consolidated as they now are, thus shutting out 

 the warm water from their interiors, and rendering possible 

 a wide-spread and intense glacial epoch. But this great 

 climatal change was actually brought about by the high 

 excentricity which occurred about 200,000 years ago; and 

 it is doubtful if a similar glaciation in equally low latitudes 

 could be produced by means of any such geographical com- 

 binations as actually occur, without the concurrence of a high 

 excentricity. 



A survey of the present condition of the earth supports this 

 view, for though Ave have enormous mountain ranges in every 

 latitude, there is no glaciated country south of Greenland in 

 N. Lat. Gl°. But directly we go back a very short period, 

 we find the superficial evidences of glaciation to an enormous 

 extent over thi'ee-fourths of the globe. In the Alps and Pyre- 

 nees, in the British Isles and Scandinavia, in Spain and the 

 Atlas, in the Caucasus and the Himalayas, in Eastern North 

 Am.erica and west of the Kocky Mountains, in the Andes, in 

 the Mountains of Brazil, in South Africa, and in New Zealand, 

 huge moraines and other unmistakable ice-marks attest the 

 universal descent of the snow^-line for several thousand feet 

 below its present level. If we reject the influence of high 

 excentricity as the cause of this almost universal glaciation,*" 

 we must postulate a general elevation of all these mountains 

 about the same time — for the close similarity in the state of 

 preservation of the ice-marks and the known activity of denu- 

 dation as a destroying agent, forbid the idea that they belong 

 to widely separated epochs. It has, indeed, been suggested, 



