Correspondence — G. W. Grabham. 239 



clunch was well exposed. The clay contained many glaciated pebbles 

 of clunch, but the point of interest was that the clunch beneath the 

 clay showed signs to the depth of several feet of having been dragged 

 along, for it contained hoiizontal shearing planes, and was full of 

 slickensides. The mechanics of this kind of action is not very 

 obvious. It would not seem at first sight that this case was quite 

 analogous to that supposed by Mr. Deeley, because it was not ice, 

 but clay, which appeared in contact with the disturbed clunch. 



Now though ice may be regarded as a highly viscous fluid, flowing, 

 though slowly, like water, yet this condition cannot be predicated of 

 Boulder-clay, much less so if the clay were frozen. But if it were not 

 frozen, and was dragged along by a deep layer of ice that covered it, 

 it can hardly be supposed that the ice communicated its own motion 

 to the whole thickness of the plastic Boulder-clay, and through it to 

 a considerable .depth of solid clunch besides. Or was the clunch 

 disturbed by the ice itself, in accordance with Mr. Deeley's 

 suggestion, before any ground moraine had reached the locality? 



The subject is worth investigation, and I would advise Cambridge 

 geologists to keep a look out for the section being again exposed, or 

 possibly to get it reopened for the purpose of examining it. A. man 

 with a pick and shovel could do it in an hour or so. 



0. ElSHEK. 



Geaveley, Huntingdon. 

 April 19, 1911. 



'FACETTED PEBBLES' AND ' DEEIKANTER '. 



Sir, — The reviewer of Messrs. Lake & Bastall's Text-Book of 

 Geology (Gteol. Mag., February, 1911, p. 85) states that the use 

 of ' dreikanter ' and ' zeugen ' is pedantic and ill calculated to 

 advance knowledge, and evidently considers that the expressions 

 ' facetted pebbles' and 'tabular outliers ' are equivalent, or " sufficient" 

 as he calls it. Apart from the reviewer being wrong in both cases, 

 the terms are recognized and used by geologists of many nationalities, 

 and it is surely desirable in a textbook to employ standard words 

 Avhich the advancing student is likely to meet with elsewhere. 

 If the suggestion of the reviewer were adopted and carried to its 

 logical conclusion, the already considerable obstacle of language 

 would be increased by each nation having its own set of scientific 

 expressions. 



A pebble may be facetted by glacial action, but there are characters 

 which would often enable us to distinguish it from a dreikanter. 

 The selective action of the wind-blast on softer parts of the rock 

 may produce furrows, but these are not to be confused with 

 glacial striae. 



A zeuge may take the form of a tabular outlier when it is formed of 

 horizontal strata, and then only if there is a suitable arrangement 

 of hard and soft beds. In country of massive, folded, or crystalline 

 rocks the zeugen would not be tabular and ' outlier ' a misnomer. 

 I have just had the privilege of traversing some 800 miles of desert 

 with no less an authoritv than Professor Walther, and in the course of 



