634 



NATURE 



[February 12, 1920 



of which produce good soils and often maintain 

 permanent wells, whereas the metamorphic rocks, 

 which form the foundation of the country, yield a 

 barren sandy soil and may have no permanent 

 water. 



The contrasts between the types of country on 

 these three kinds of rock are so striking that an 

 aeroplane observer would soon learn to distin- 

 guish them and thus discover potential oases on 

 lava or limestone in the wastes of sandy scrub. 

 In such countries travel to a physiographer is 

 often as exasperating as the sudden interruptions 

 of view along a railway by lines of obstructive 

 trees, cuttings, and tunnels, which led Ruskin to 

 renounce railway travel, . on the ground that he 

 would as soon thus hasten a journey across inter- 

 esting country as an epicure would compress his 

 meal into a single pill. Moreover, the traverse of 

 these arid plains in the dry season is hazardous, 

 as a caravan strong enough for necessary trans- 

 port and defence is liable to disaster by failure to 

 find water ; whereas an accompanying aeroplane 

 scout would at once discover any remaining water- 

 holes, which might be concealed from a caravan 

 passing a short distance from them. Aeroplane 

 guidance might thus enable an expedition to cross 

 an area which otherwise it would be foolhardy to 

 enter. 



The motor-car is no doubt of great service on- 

 these plains in dry weather, but its use is attended 

 with the serious danger that a sudden fall of rain 

 may convert the country into a sea of mud, in 

 which the motor is immovable. A premature rain- 

 storm before the normal rainy season may leave 

 a party dependent on motor transport as com- 

 pletely isolated in the desert as a shipwrecked 

 party on an oceanic island. 



African geography is in a stage when bird's-eye 

 views may be very instructive. For example, 

 south-west of Lake Stefanie different explorers 

 have reported lines of hills and scarps the inter- 

 pretation of which is at present uncertain ; but to 

 an aeroplane observer surveying the country, espe- 

 cially when helped by the long shadows of early 

 morning or late afternoon, these lines would 

 appear in such diagrammatic outline as to give 

 him an insight into their relations, which would 

 cost a traveller on foot an arduous season's cam- 

 paign. Similarly, there is much difference of 

 opinion as to the connection between Lake Nyasa 

 and the southern end of the Rift Valley in central 

 " German " East Africa near Kilimatinde ; the 

 Ruaha Valley overlaps with a relief line to the 

 north-west of it, but no connection between them 

 has been recognised. An aeroplane survey of this 

 region under suitable illumination would 

 demonstrate the structural relations between the 

 chief features in the relief of the area with a speed, 

 an ease, and an economy which no other method 

 could approach. Again, in the area which the 

 Times expedition will skirt in going from Tangan- 

 yika to the mines at Broken Hill, the structural 

 geography is complex, including valleys and scarps 

 of different dates and plateaux of sandstone of 

 various undetermined ages. The traverse of this 

 NO. 2624, VOL. 104] 



district is arduous, and comprehensive views across 

 it are difficult to obtain. But a survey or looking 

 down on it, especially if able to hover over it at 

 leisure and see it from different angles and under 

 various conditions of illumination, would probably 

 contribute greatly to the solution of its leading 

 tectonic problems. 



Dr. Chalmers Mitchell's traverse, being an 

 experimental journey, will probably be unable to 

 make many deviations for scientific study, but it 

 is following a route of exceptional interest, and 

 we may expect light from him on some East 

 African physiographic problems, such as the con- 

 troversy as to whether the Lower Nile \'alley is 

 a down-folded basin or a down-faulted trough, or 

 as to the relations of the young valley which the 

 Nile is excavating north of Khartum to the older 

 river which drained that area. His survey of the 

 northern face of the plateau north of Uganda, 

 seen from a distance which will blot out the minor 

 irregularities, may throw light on its origin ; and 

 during his flight from Nimule to the A'ictoria 

 Nyanza he may discover some line of depression 

 continuing the tectonic subsidence north-east of 

 the Albert Nyanza towards Lake Rudolf. In addi- 

 tion to work of this character, enabling Africa to 

 be studied like a great relief model, the value of 

 the aeroplane in scientific work will probably be 

 mainly as a means of rapid transport to centres 

 for study or help in emergencies. 



The cost of aeroplane transport may seem large 

 when compared with railway rates of a penny per 

 ton-mile ; but it is insignificant in comparison with 

 that of a caravan across a foodless territory, when 

 each porter can carry so little in addition to his 

 food that the cost of the carriage of goods from 

 Mombasa to Uganda was reckoned at 300L a ton. 

 The aeroplane will doubtless enable the arid areas 

 in East Africa to be investigated at a much 

 cheaper rate than any other available method. 



In the political administration of Africa, Dr. 

 Chahners Mitchell's mission may lead to ultimate 

 economy in many districts. Thus, in northern 

 British East Africa, garrisons are so isolated, and 

 so liable to sudden calls to control the nomads or 

 to resist Abyssinian raids, that they must be main- 

 tained at costly strength ; but a periodic aeroplane 

 inspection of the desert lands on the borders of 

 British East Africa would reveal the whereabouts 

 of the tribes and discover whether there were any 

 concentrations of men and camels which threat- 

 ened mischief; and thus it would add greatly to 

 the efficiency of the frontier guard. 



From its bearing on African administration, on 

 an accelerated postal service, on quicker and 

 cheaper transport of oflScials and investigators, as 

 well as for its direct observations, the journey of 

 Dr. Chalmers Mitchell and his companions may 

 mark the beginning of a new epoch in African 

 travel. J. W. Gkegorv. 



(3) Civil Aviation. 



The lecture bv Major-Gen. .Sir F. H. Svkes on 



"Imperial Air Routes," which was delivered before 



the Royal Geographical Society on February 2, 



will be earterly read bv all interested in the future of 



