SURVEYS AND MAPS 57 



tion, and geological features, such as outcrops, faults, dykes, and 

 sometimes even the location of mineral resources which would be 

 unnoticeable to the ground worker, can be seen at a glance by the 

 expert. The differences in soils can often be revealed by the actinic 

 eye of the camera, and recent work in Australia has shown that on 

 flat plains much can be learned concerning underlying geological 

 structures by studying soil in this way. The type and extent of 

 native agriculture and the location of native villages can also be 

 seen at a glance. 



As a particular example, though not from Africa, reference may 

 be made to the recent air survey of the forest-covered Irrawaddy 

 Delta, carried out in 1924 (Kemp and others 1925). The total cost 

 was under Rs. 300 per square mile compared with about Rs. 500 

 for ground work which would have given no indication of forest 

 types. The time for all stages did not much exceed one year com- 

 pared with some three to four years on the ground. The Irrawaddy 

 Delta is far more favourable than most of Africa by reason of its 

 lack of ground relief, but the example shows the advantage of air 

 survey under suitable conditions. 



The only air survey carried out by Government in British Africa 

 has been in Tanganyika, where an Air Survey Section was esta- 

 blished in 1 93 1. Since then, most of the important townships and 

 harbours have been photographed, and in 1934 assistance was 

 given to the Zanzibar Government in taking air photographs 

 for town-planning and cadastral purposes (Tanganyika 1933, 

 D.R.). 



The principal companies which have operated in Africa to date 

 are: H. Hemming & Partners, Ltd., who, through the agency of 

 their operating companies, Geological Air Surveys, Ltd., and 

 African Air Surveying Co. (Pty.) Ltd., have carried out extensive 

 operations in South Africa, principally for mining companies. An 

 air survey of the Witwatersrand Reef is in progress at the moment. 

 Mr, H. Hemming (1933 and 1934, etc.) has written a number of 

 articles stressing the value of air work both in mapping and in 

 revealing natural resources. The Aircraft Operating Company, 

 Ltd., and the Aircraft Operating Company of Africa, Ltd.,* have 



* This branch company with headquarters at Johannesburg is now in the charge 

 of Mr. Robbins who has stressed the value of air photographs in plant ecology and 

 whose work in this connection is mentioned in Chapter vi. 



