190 [Proc. B.N.F.C., 



Wicklow, Kerry, and Connemara. Many speculations have 

 been on foot as to the conditions which could lead to such a 

 marvellous extension of ice. The earlier ones, following the 

 well-known principles of Lyell, sought to find in changes in the 

 position of sea and land and in the diversion of ocean currents, 

 such as the Gulf Stream, a sufficient explanation. Every 

 geologist will always freely admit the great influence which 

 such changes must always have upon local climate, and which 

 is amply proved by a comparison between the present condition 

 of Labrador, for instance, cold, bleak, and infertile, and Norway, 

 with its smiling, tourist-frequented valleys, or between Green- 

 land, smothered under a dome of ice, and the middle of Siberia, 

 the plains of which, in spite of the winter cold, are covered 

 with flowers every summer, as well as between the northern 

 and the southern hemispheres generally, which latter, although 

 actually nearer the sun in summer than ourselves, is yet 

 undergoing at present a modified glacial epoch. Whilst admit- 

 ting all this, many have felt that some more far-reaching cause 

 would have to be sought for. This the late Mr. Croll claimed 

 to have found, and has set forth in his remarkable work 

 " Climate and Time." Croll's theory has been adopted by Sir 

 Robert Ball, and the eminence of his name has now led to its 

 being often called Sir Robert Ball's theory. Most of you are 

 familiar with it, and I need not spend time over it this evening. 

 I will only remark that, notwithstanding the convincing nature 

 of its demonstration, some recent geologists have challenged it, 

 apparently on the ground that it puts the last glacial epoch (if 

 there have been more than one) too far back, 70,000 or 80,000 

 instead of, say, about 10,000 years. Perhaps the most interesting 

 battle of the next few years amongst geologists will be between 

 the advocates of a great ice sheet and the advocates of a great 

 submergence, with merely a system of local glaciers. It must 

 always be remembered, however, that the greater the submerg- 

 ence of the land the less room would be left for an accumulation 

 of ice sufficient to give rise to large glaciers capable of detaching 

 numerous bergs. Again, some persons may recollect how a few 



