350 



R. W. COPPINGER ON SOILCAP-MOTION. 



lakes, and sea-margins, and was especially important as showing how 

 some phenomena ordinarily attributed to ice could be produced. 



Mr. TJssher asked what the nature of the subsoil was. 



Mr. Fordham asked for information as to the origin of the soil- 

 cap, and its formation on the high ground from which it was stated 

 to be slipping. 



Mr. Hawkshaw remarked that engineers, to their cost, were well 

 acquainted with the unstable condition of the soilcap. Small dis- 

 turbances often set in motion large masses not only of clays but of 

 rocks. Good examples of rock-movement might be seen on the 

 Bipponden branch of the Lancashire aud Yorkshire Railway. The 

 surface once disturbed, continued to move for long periods. In some 

 railway- cuttings the slopes had moved for twenty years. 



Mr. Spkatlino called attention to the slipping of clay in the 

 Erockley cutting, near new Cross. 



Mr. Hudleston said this paper supplemented Sir Wyville Thomson's 

 observations on the " stone rivers " of the Falkland Isles, where he 

 explained the accumulation of quartzite blocks by this kind of slip- 

 ping. Such observations tended to show how some of the old 

 brec ciasmight have been formed by other agencies than that of ice. 



