us 



ISLAND LIFE. 



[part I. 



glaciation when moraines were left in the valleys; several 'Succes- 

 sive periods of submergence and elevation, the later ones becom- 

 ing less and less in amount, as indicated by the raised beaches 

 slightly elevated above our present coast line ; and lastly, the 

 occurrence in the same deposits of animal remains indicating 

 both a warm and a cold climate, and especially the existence 

 of the hippopotamus in Yorkshire soon after the period of 

 extreme glaciation. 



But although the evidence of so^ne alternations of climate 

 seems indisputable, and no suggestion of any adequate cause 

 for them other than the alternating phases of precession during 

 high excentricity has been made, it by no means follows that 

 these changes were always very great— that is to say, that the 

 ice completely disappeared and a warm climate prevailed 

 throughout the whole year. It is quite evident that, during 

 the height of the glacial epoch there was a combination of 

 causes at work which led to a large portion of North-western 

 Europe and Eastern America being buried in ice to a greater 

 extent even than Greenland is now, since it certainly extended 

 beyond the land and filled up all the shallow seas between 

 our islands and Scandinavia. Among these causes we must 

 reckon a diminution of the force of the Gulf Stream, or its being 

 diverted from the north-western coasts of Europe ; and what we 

 have to consider is, whether the alteration from a long cold 

 winter and short hot summer, to a short mild winter and long 

 cool summer would greatly affect the amount of ice if the 

 ocean currents reraained the same. The force of these currents 

 are, it is true, by our hypothesis, modified by the increase 

 or diminution of the ice in the two hemispheres alternately, 

 and they then react upon climate ; but they cannot be thus 

 changed till after the ice-accumulation has been considerably 

 affected by other causes. Their direction may, indeed, be 

 greatly changed by slight alterations in the outline of the land, 

 while they may be barred out altogether by other alteriitions 

 of not very great amount ; but such changes as these have no 

 relation to the alteration of climates caused by the changing 

 phases of precession. 



Now, the existence at the present time of an ice- clad 



