DISCOVERY 



171 



fields of a group of communitit-s which ceased to exist 

 about 1,500 years ago. Remains of the vUlages where 

 lived the people who cultivated these fields can still 

 be seen upon the downlands of Wessex and Sussex." 

 The essential function of air photography is that it 

 makes evident the plan and arrangement of ancient 

 fields and roads which, from the ground, appear only 

 as broad banks with no definite arrangement. Their 

 relation to remains of known Roman origin proves that 

 they were in existence before the Roman conquest. 

 They prove that agriculture was well developed in 

 southern England long before that event. Moreover, 

 it is evident, from the isolated round white spots due 

 to localised patches of chalk, that the custom which 

 still persists of "marling " or fertilising the fields with 

 chalk brought from a distance was established in very 

 ancient times. These cultivations, the author believes, 

 were the works of Celtic communities ; the Saxons 

 preferred the rich vallej's by the streams. It is 

 strange to read of the long-forgotten relics of ancient 

 days brought to light by the aid of one of the 

 newest of scientific methods — air photograph}-. Above 

 all, these discoveries serve to emphasise again the 

 antiquity of the downland, and its grandeur, unspoilt 

 as yet by all the artificiality and commercial develop- 

 ment of modern England. 



" But here the old Gods guard their round, 

 And in her secret heart 

 The heathen-kingdom Wilfrid found 

 Dreams, as she dwells, apart." 



H: ^ ^ ^ ^ 



We feel that the importance, even greater to all who 

 love their native land and its graduallj' vanishing 

 countryside than to the specialised interest of the 

 archaeologist, of restraining the hand of the spoiler 

 in the shape of the advertiser, justifies a reference in 

 this place to the Bill now before Parliament to curtail 

 his activity. A peculiarly offensive example is to be 

 seen, carved in the chalk outside Lewes, in the heart of 

 Downland, in letters many yards long. It is a most 

 unpleasing experience to walk from the Long Man of 

 Wilmington, carved in the chalk unknown hundreds 

 of years ago, to this modern atrocity. We trust that 

 the Bill will safely make its way through the devious 

 routes of Parliamentary procedure, and take effect at 

 an early date. Surely the feeling of antagonism in- 

 spired by the thoroughly distasteful exhortation to 

 purchase some commodity must completely out- 

 weigh the advantage of any publicity so gained. Un- 

 fortunately, a determination never to purchase any 

 article so recommended would quickly prevent a public- 

 spirited individual to-day from buying anything, so 

 widespread is the habit. But, short of legislation, such 

 a course seems the only logical way to set a term to the 

 nuisance. 



The Structure of the 

 Earth 



A New Theory 



By O. H. T. Rishbeth, M.A. 



Reader in Geography in the Sonthamptun Universily College 0/ Wessea; 



This is the century of world views and world vision 

 in matters of business, social construction, and 

 politics ; it is also the century of world aspects in 

 matters intellectual, in history, economics, and, not 

 least, in geography and geology. There is a growing 

 interest in problems connected with the physical 

 nature of our world as a whole, its composition, 

 structure, the distribution of elements in and upon 

 it, and the reasons for that distribution. Recently 

 prominence has been given in discussion to Wegener's 

 theory- — the theory of the drifting apart of continents. 

 It may be of interest to acquaint ourselves with 

 another theory, even more ambitious in its scope, 

 which will perhaps come prominently into notice, and 

 which bears the marks of greatness. The theory is 

 the result of " long years of study in the field and in 

 the literature of the subject," and its author, since the 

 appearance of the book in which he sets it forth, has 

 been appointed to one of the most important chairs 

 in his subject on the Continent. 



The problem of motnitain-building has long occupied 

 the minds of thinkers, and its connection with the 

 equally absorbing subject of the nature and structure 

 of the ocean basins has become increasingly emphasised. 

 The Pacific is bordered by chains, the apparent 

 remnants of a mighty mountain girdle. The great 

 Eurasiatic moimtain-zone breaks off east and west 

 into oceans, is flanked by flooded hollows almost 

 throughout its length, and is never far from the ocean. 

 Nearly all the great mountain systems, old or young, 

 are contiguous to continental margins,' while the 

 hearts of the continents are relatively imdisturbed. 

 The existence of mountains and orographical features 

 generally on the ocean floors has long been recognised, 

 and although the whole subject remains a field of 

 conflicting theories, the great oceanic troughs (geo- 

 synclines) are frequentlj' regarded as the wombs or 

 the graves of mountains. 



Kober builds with existing materials. His method is 

 evolutionary rather than revolutionary : he absorbs, 



' L. Kober, Der Ban der Erde (Geb. Borntraeger, Berlin, 

 1921). 



- For an exposition of this theory by Professor Wegener 

 himself, see Discovery, vol. iii. No. 29. 



^ The main exceptions (e.g. Altai and other Central Asiatic 

 block-mountain systems) are more apparent than real. (Vide 

 infra.) 



