Mr. G. Tate on Glaciated Rocks. 239 



Alnwick and Bilton. The position of one block was pecu- 

 liar ; it was mountain limestone of a light drab colour, four 

 feet long by three feet three inches high and three feet 

 broad; it penetrated about one foot into an irregularly 

 stratified gravel, which was five feet in thickness and com- 

 posed entirely of water- worn rounded stones, many of which 

 had come from a distance; it passed through a stratified red 

 clay fifteen inches in thickness, and it was sunk about one 

 foot into fine stratified sand. 



When the Club met at Greenlaw in 1864, one large block 

 with a glaciated surface was detected in the railway cutting 

 near that place ; and as the deposit in which it was found 

 appeared an extension of the lower beds forming the kaims, 

 the observation possesses some interest. In Northumberland, 

 the ridges at Chathill, Newham, and Hoppen are similar to 

 the Berwickshire kaims but of smaller extent ; and in these, 

 I have recently found a few glaciated rocks, among the water- 

 worn gravel and sands of which these minor kaims are prin- 

 cipally composed. 



To theorise on these facts is not my intention at present ; 

 but I may briefly state, that geologists generally have given 

 up the hypothesis which attributed them to the action of 

 great debacles or violent rushes of water. Neither polishing 

 nor strise are produced by floods, flowing over rocks, or 

 driving before them stones or mud. Stones are smoothed by 

 attrition as they are rolled along, but they are never polished 

 or striated. Great blocks transported down the glens of the 

 Cheviots, by the tremendous water-falls from the hills, bear 

 upon them no such marks. I have examined the effect of 

 the highest tides and greatest storms on our coast ; but 

 though I have seen evidences of masses of strata broken 

 down and swept away, and great blocks many tons weight 

 driven over other rocks considerable distances, yet no traces 

 of polishing or striation could be seen. So far as is at present 

 known, ice is the only agent which produces such effects; 

 not only do the glaciers on the Alps, in Iceland, and other 

 mountain regions polish and striate the rock surfaces over 

 which they move ; but even the ice-covering of an extensive 

 area of land, with a gentle slope, such as Greenland, pro- 

 duces similar effects, by slowly moving down to the sea 

 shore ; and it may be inferred that the great icebergs, some 

 of which are four miles in circumference and eighteen hun- 

 dred feet in height, when grounding and moving over the sea 

 bottom would also polish and striate rock surfaces. 



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