ANCIENT GLACIERS IN EASTERN HEMISPHERE. 153 



among other varying factors — by the draught of the berg. 

 A mass of small draught will be carried by surface cur- 

 rents, while one of greater depth will be brought within 

 the influence of under-currents ; and hence it not infre- 

 quently happens that while floe-ice is drifting, say, to the 

 southeast, giant bergs will go crashing through it to the 

 northwest. There are tidal influences also to be reckoned 

 with, and it is matter of common knowledge that flotsam 

 and jetsam travel back and forth, as they are alternately 

 affected by ebb and flood tide. 



" Bearing these facts in mind, it is surely too much to 

 expect that marine ice should transport boulders (how it 

 picked up many of them also requires explanation) with 

 such unfailing regularity that it can be said without chal- 

 lenge,* ' boulders in this district [South Lancashire and 

 Cheshire] never occur to the north or west of the parent 

 rock.' The same rule applies without a single authentic 

 exception to the whole area covered by the eastern branch 

 of the Irish Sea Glacier ; and hence it comes about that 

 not a single boulder of Welsh rock has ever been 1 ecorded 

 from Lancashire. 



" The Solivay Glacier. — The pressure which forced 

 much of the Irish Sea ice against the Cumbrian coast-line 

 caused, as has been described, a cleavage of the flow near 

 Ravenglass, and, having followed the southerly branch to 

 its termination in the midlands, the remaining moiety de- 

 mands attention 



" The ' easting ' motion carried it up the Solway Frith, 

 its right flank spreading over the low plain of northern 

 Cumberland, which it strewed with boulders of the well- 

 known ' syenite ' (granophyre) of Buttermere. When this 

 ice reached the foot of the Cross Fell escarpment, it suf- 

 fered a second bifurcation, one branch pushing to the 

 eastward up the valley of the Irthing and over into Tyne- 



* Brit. Assoc. Report, 1890, p. 343. 



