12 Jackson, Facetted Pebbles with Glacial Deposits. 



Possibly there were more frequent variations in temperature during 

 the period when these lay exposed at the surface of the Drift. 



Dr. Bather, in his exhaustive paper on the subject of wind- worn 

 pebbles {op. cit., p. 401), refers to several writers who have attempted 

 to explain at all events the main contours of facetted pebbles as due 

 to the breaking up of rocks into angular fragments, but, he goes on 

 to say, " we have yet to learn of a rock in which the joint-planes lie 

 at the angles usual in pebbles facetted by blown-sand." The series 

 dealt with in this paper show that such cases are definitely present 

 (see Figs. 4 and 9). They also show that a typical Dreikanter form 

 can be produced in this way. Though all the pebbles from the zone 

 exhibit evidence of sand-blast, either in the form of polish or erosion, 

 there is little evidence that any large face has actually been produced 

 by wind and sand action. 



We can now turn our attention to the interesting feature of 

 wind-erosion and to a consideration of its significance. It has been 

 argued by several writers on- the subject that wind-worn pebbles 

 imply desert, or, at least, steppe conditions. They have also been 

 regarded as indicating uniform climatic, as well as geological rela- 

 tions, and that the conditions leading to their production must 

 therefore have a similarly general significance. These statements 

 are not altogether borne out by the evidence provided by the numer- 

 ous occurrences, for, as Bather remarks {op. cit., p. 411) : " Facetted 

 and wind-polished pebbles have been found over almost all parts 

 of the present surface of the earth, under tropical, temperate, and 

 Arctic climates, on plains, on hills, or in valleys, scattered over 

 steppes and deserts, or confined to small clearings in the midst of 

 fertile fields and evergreen forests." He gives a list of a few recorded 

 localities, as follows : — deserts of Libya and Arabia ; desert of Sinai ; 

 Kalahari desert of S.W. Africa ; 16 kilometres from Walfisch Bay, 

 S. Africa ; deserts of Central Asia ; Reval ; Schleswig-Hoistein ; 

 Jutland ; Anholt in Kattegat ; Silfakra, near Lund, East Scania 

 and N. of Fjelkinge, near Kristianstad ; Halland ; Iceland ; sandy 

 plateau of Brenne, in France ; surface of old moraines near Lyon ; 

 New Zealand, various localities x ; California ; Colorado ; Nebraska, 

 Bad Lands ; New Jersey and Northern New York. To these are 

 to be added the numerous localities in Germany, recorded in 

 the papers by Berendt, Chelius, Geinitz, Gutbier, Wittich, and 

 others. 2 



In Germany, it is true, facetted pebbles are scattered over a 

 wide area, and their intimate association with the Loess, with its 

 peculiar fauna, seems to imply a dry climate or steppe conditions, 

 following on the retreat of the glaciers, when the North German 

 Plain was covered with loose deposits as yet uncovered with vegeta- 

 tion. But the evidence in favour of steppe conditions obtaining in 



1 It is interesting to note that among the wind-worn pebbles from the 

 Waitotara Grand Flats, near Wanganui, New Zealand, in the Manchester 

 Museum, are one or two showing the beginning of wind-erosion on fractured 

 su rf aces. 



2 See Bather's paper, op. cit., for references to literature. 



