18 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [May 17, 



boulders were transported by the moving body which produced the 

 scratches. 



From the difficulty, if not impossibility, of accounting for these 

 furrows except by glacial agency, and from the marked resemblance 

 which the till bears to the moraines left by ancient glaciers in Switz- 

 erland, it has been concluded that the cause of both deposits was 

 the same. A careful examination of the Swiss moraines, however, 

 satisfied me that they are essentially different. We have in both cases 

 a confused assemblage of fragments of rock and earthy matter thrown 

 together without regard to gravity, and in both cases the erratic 

 blocks are found to have come in a certain direction ; so far the re- 

 semblance is complete : but in Scotland we find that the blocks be- 

 come rounded, and diminish in size as they recede from the parent 

 rock : in ancient moraines they do neither : there is nothing in fact, 

 either in glaciers or in icebergs, to round the blocks they bear along 

 with them, or to reduce them in size. The conditions therefore re- 

 quired, before we can admit that blocks have been transported by 

 glaciers, are, angularity, a given direction, and no apparent diminution 

 in size. Those which have fallen from icebergs ought to have the 

 same characters, except as to definite direction ; they ought also to 

 be superficial. It appears to me, that the phaenomena presented by 

 the till could only be produced by the tumultuary and transient ac- 

 tion of water. 



Supposing this to be the case, could blocks impelled by a sudden 

 rush, such as an earthquake-wave, produce the scratches ? Without 

 denying the possibility of their doing so in any case, I do not con- 

 sider it possible in the present one — the strise are too regular. A rock 

 in the immediate neighbourhood of the above-mentioned boulders 

 may truly be called a " roche polie ;" and in one place there is a furrow 

 eighteen inches broad and six inches deep, which could not possibly 

 be caused by a rolling mass. 



The scratched rocks pass under the sea ; I do not however consider 

 this as a proof of the recentness of the scratching process, but of a 

 recent subsidence of the land. 



Part II. 



[Read May 17, 1848.] 



Although I have not attempted to explain the particular pheeno- 

 mena described in the former part of this paper, I think it must be 

 admitted, that the scratches and furrows on rocks and boulders must 

 in many instances be ascribed to glacial action either in the shape of 

 icebergs or glaciers. 



If we suppose that the temperature of Great Britain was as low at 

 the period to which we must ascribe them, as it is in other quarters 

 of the globe at present, under correspondent latitudes, — and there is 

 no antecedent improbability in the supposition, — then ice under both 

 forms must have been in action. Let us inquire what would be the 

 effects of such a state of things ? In a period of geological repose, 

 glaciers would scratch the rocks on the sides and bottoms of their 



