220 Prof. Hughes, Criticism of the Geological [Oct. 30, 



might be undermined and the debris sink into the deeper hollows 

 without much washing and sorting of the material or any destruc- 

 tion of the glacial mar-kings, and thus give rise to the supposition 

 that the glaciers once descended to the sea. It needs much more 

 evidence and an answer to several obvious questions before the 

 inference as to the former descent of the glaciers to sea-level can 

 be accepted as satisfactory. Has it in any case been shown that 

 the fauna of the deposits associated with the Carboniferous or 

 Permian boulder beds has an arctic or even a more northern facies 

 than that which occurs in beds of approximately the same age 

 elsewhere ? Certainly not in the case of the conglomerates at the 

 base of the Carboniferous rocks of this country, where large corals 

 grew among the boulders, while in other beds of the same series 

 the same corals are associated with the remains of a tropical 

 vegetation. 



Further, assuming that the boulders referred to are really of 

 glacial origin and certainly in place, before we can accept them as 

 proof of extreme glacial conditions on the site and at the level 

 where they are now found, we must examine the various ways in 

 which nature transports glaciated boulders and other drift, far 

 beyond the region of original glaciation without calling in the aid 

 of earth-movements to depress glaciated hill-tops to sea-level. 



The start of the boulders is interesting but need not take long. 

 They fall on the upper ice and, where the ice goes, there they are 

 carried as long as they remain on it or in it and if the journey be 

 long on a glacier^ most of them will get into the crevasses and 

 eventually find their way to the bottom, where some will be 

 washed down in glacier streams and some help to grind the other 

 included stones and the solid rock. 



When they get to the end of the glacier all polish and striae 

 are soon lost in the streams that flow from it unless the ice breaks 

 off in a lake or in the sea when it will bear its burden of drift 

 about till it is melted down into too small a raft for the load and 

 then the whole will go to the bottom. 



The question we are now considering is not how high must 

 the land have been for the snow to accumulate and turn to glacier 

 ice in any part of the tropical or temperate regions, nor how near 

 the equator may glaciers have come down to the sea, nor how near 

 to the sea may they have occurred provided there were a great 

 uplift of mountain ranges and abundant precipitation, but we will 

 now confine our enquiry to the mode of transport after the boulder 

 or drift has been launched. 



Within the last few weeks the story of icebergs in the South 

 Atlantic in latitude 54° has been going the round of the papers. 



1 "Notes on the Geology of Parts of Yorkshire and Westmorland," Geol. 

 Polytech. Soc. W. Riding, Yorks., July 17, 1867, p. 11. 



