118 Prof. Hughes, Criticism, of the Oeological [Oct. 30, 



xvi. Conclusion. 



I have in this the first part of my communication confined my 

 attention to the evidence derived from the character of the 

 fragments contained in glacially transported deposits and of the 

 rock over which the ice has passed. That is to say I have con- 

 sidered only the polishing and striation of the boulders and of the 

 solid floor. The question I have kept before me has been always, 

 Can such a condition of the surface have been produced in any 

 other way than by the agency of ice ? and I have exhibited a 

 series of specimens to illustrate the view that there are many 

 different operations of nature by which polished and smoothed 

 and striated surfaces can be produced, that some of them can in 

 certain cases be distinguished from those due to ice action, but 

 that many of them, especially when weathered, exhibit the 

 " ghosts of scratches " undistinguishable from those left on glacial 

 boulders. I have incorporated a large number of specimens 

 simply in explanation of the manner in which certain conditions 

 of the surface are produced, irrespective of the question whether 

 the particular agent artificial or other that did in that particular 

 case produce them can have existed in past ages or in arctic 

 climates. 



I have then criticised the principal cases in which it has been 

 contended that we have evidence of glacial action in ancient 

 boulder deposits, and have shown, by reference to actual specimens 

 of the rocks in question, that, not only is the evidence of palaeo- 

 zoic or mesozoic glaciation in Britain inconclusive, but that the 

 negative can be proved in all the cases hitherto adduced. 



Being thus warned against taking on trust evidence for glacial 

 action in ancient times founded upon the form or the condition 

 of the surface of the rock, I venture to throw doubt on the 

 inference that the faceted stones of Copitz by Pirna are of 

 glacial origin. I give the results of some of my own explora- 

 tions among the ancient boulder clays of Wetzikon, &c. I point 

 out that the Cambrian scratched stones of Norway are in regions 

 still under the influence of glacial conditions in spite of the mild 

 influences of the gulf stream. I then give a sketch of the dis- 

 tribution of boulder-bearing beds in India, Australia and Africa, 

 but have no evidence from personal observation to offer respecting 

 them. I admit that the consensus of many competent observers 

 renders it difficult to believe that these beds do not exhibit 

 evidence of glacial origin. 



Another question must however be carefully examined before 

 we can accept the view that glaciers came down to the sea in the 

 region where these boulders have been discovered, that is, the 

 mode of transport of boulders. First, how far from their starting 

 point at the land -ice foot may they have been carried by floating 



