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making deductions as to the nature of drift deposits from the land forms in 
which they occur. 
4. Mechanism of development and stratigraphic age 
Apart from facilitating the geomorphological study of the areas in which 
patterns occur, it is not yet obvious how air photography is able to facilitate 
this part of the study. 
Limitations of Air Photography 
In spite of the considerable value of air photography, it is important to 
stress the following limitations: 
1. Much of the routine vertical cover has been flown at the wrong time of the 
year. Soil patterns are best observed on cover flown between February and 
April; vegetational and crop patterns usually are most easily seen between 
March and July. However, for an academic study of this type the cost of 
special cover would be prohibitive. 
2. The patterns do not always show up on air photographs even when the 
subsoil features are present. The technique is thus not entirely reliable for 
reconnaisance and plotting. 
3. Fine details of micro-relief and of vegetation patterns are normally only 
observable using conventional methods of topographical and ecological 
survey in the field. 
References 
Baden-Powell, D. F. W. (1948). The Chalky Boulder Clays of Norfolk and Suffolk. Geol. 
Mag. 85, 279-96. 
Perrin, R. M. S. (1955). Studies in Pedogenesis: Pt. 2. On Calcareous Till in the Breckland 
Ph. D. Thesis. University of Cambridge. 
Watt, A. S. (1955). Stone stripes in Breckland, Norfolk. Geol. Mag. 92, 173-4. 
West, R. G. (1962) (In the press) Problems of the British Quaternary. Proc. Geol. Assoc. 
London 73. 
Discussion 
Mr. J. L. Retzer (U.S.A.): 1. What are the clay mineral types? 2. Has ice wedging been 
considered? Answer: 1. The clay mineral assemblage is probably unimportant, as the soils 
concerned are extremely sandy (clay contents as low as 0,5%). 2. Yes, the patterns are certain 
ly of periglacial origin. However, the speaker did not wish to equate them with any others 
until he had more data. 
Mr. R. F. Tomlinson (Canada) noted that similar patterns have been observed in Canada, 
most commonly on clay soils. They are, in fact, used as a broad photo-indicator of a clay soil. 
Dr. Perrin was fairly certain that disturbances, similar to those he has shown, are present in 
many places in soils of heavy texture. It is, however, noteworthy that in these cases they are 
not readily observed on aerial photographs. 
Several of those present drew attention to conformations similar to the patterns discussed. 
Prof. Radforth (Canada) and Dr. Vink (Neth.) mentioned cases where they are found under 
what are still periglacial conditions (resp. Ellesmere Island and Greenland) whereas Mr. 
Grove (U.S.A.) mentioned Kansas and Oklahoma where they, probably wrongly, have been 
described as gilgai.