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



vi. Rocks striated hi/ other than glacial agency. 



If the solid rock or any stone firmly fixed in its place have 

 another mass holding minerals hard enough to groove the surface 

 drawn across it, the result must be the same whether it be ice or 

 any other material that clasps the stone or holds the rasp. For 

 instance, if trees be dragged down a hill side, bits of grit get 

 driven into the wood and as it passes over the solid rock they cut 

 striae exactly like those produced by glacial action as may be well 

 seen on No. 28 and No. 29 which is part of a mass of Jurassic 

 Limestone which stuck out in the road up the Jura from Grenchen 

 to Blirenberg in the canton of Solothurn (Soleure). The grit 

 imbedded in the wood and the carts with breaks and skids have 

 grooved and scratched the stones so that the exposed parts can 

 hardly be distinguished from glaciated surfaces, as may be seen 

 by comparing No. 28 with No. 5 which is a genuine glaciated 

 rock from the same district. 



The effect of dragging timber down a hill side is well shown 

 also on Nos. 30 and 31, two specimens of Silurian rock from near 

 Corwen. 



Some examples it may be pointed out cannot be offered in 

 explanation of possible modes of producing surfaces simulating 

 those due to glacial action as they are due to the agency of man 

 or other forces which cannot have been in activity at the time. 

 But any case in which the mode of operation is certainly known 

 and the results can be closely studied are of value in such 

 enquiries. 



For instance there is a quarry at Rhiwallt near St Asaph in 

 which the Silurian rock has been removed along the planes of 

 bedding so that a long sloping face has been left, down which 

 slide broken rock and masses of earth with stones imbedded, 

 marking their path on the face of the rock as seen in No. 82 and 

 No. 33. Though in this case the face of rock was exposed by man, 

 the same kind of thing must often have occurred at every period 

 of the world's history and stones and gritty material have slid down 

 over long faces of bare rock into deep water and so produced all 

 sorts of difficult complications. 



More distinctly due to artificial operations, but most instruc- 

 tive from the deep grooves and fine polish produced, are the two 

 specimens No. 34 and No. 35 from the Mountain limestone of 

 Ribblesdale where the wire rope, dragging in places over remains 

 of drift, which was largely derived from gritty carboniferous beds 

 above, has polished and striated and fluted the rock over which it 

 has run. 



No. 36 is a glaciated face of rock but the ice marks are very 

 obscure. The obvious scratching and polishing of the rock is due 



