588 



NATURE 



[OcTOliER 15, 1 1 



large numbers have taken jilace from it. The temperate grass 

 and forest regions above 5000 feet are the only places in Africa 

 that have acted as swarming centres of population. The 

 character of the native races inhabiting them is vigorous and 

 turbulent, and raiding is often carried on. The difi'erences in 

 climate, vegetation, and abundance of wild and domestic 

 animals, explain why it is that these races only have, except in 

 one instance, resisted both -Vrab and European. 



Sir Charles Wilson gave an able and most timely discourse on 

 the geography of the Egyptian Sudan, dwelling especially on 

 the resources of the country, and the importance of opening out 

 trade-routes between the Sudan and the sea ; the best method 

 of doing which appeared to liim to be the construction of such a 

 line as the Berber and SuaUin railway. Lieut. Vandeleur read 

 an interesting account of his recent journey from Uganda to the 

 Upper Nile country, giving an excellent idea of the physical 

 geography and resources of the region, and dwelling in |5ar- 

 ticular on the difficulties to navigation caused by the floating 

 vegetable carpet or siidd which frequently blocks the rivers. 

 Amongst other slides he showed the first photographs which 

 have been taken of the Murchison Falls on the Victoria Nile. 

 The Rev. C. II. Robinson gave an account of his experiences 

 amongst the Hau.sa in the Niger district ; and Mr. H. S. Cowper 

 gave some account of a second short journey made in March 1896, 

 in the Tarhuna and M'salata districts of Tripoli. During his visit 

 he examined or noted about forty additional megalithic ruins of 

 the type called by the .\rabs Senam. The route taken was by 

 the Wadi Terr'qurt, a fine valley running parallel to the Wadi 

 Doga, by which he entered the hills in 1S95. He then pro- 

 ceeded to the districts of Ghirrah and Mamurah, south of 

 Ferjana, through whicli runs a great wadi, the Tergilat. This 

 reaches the sea at Kani, twelve miles south-east of the ruins of 

 Leptis Magna, and is undoubtedly the Cinyps of Herodotus. 

 On reaching the coast a week was spent at the ruins of Leptis 

 and the Kam district, and the return journey was made to 

 Tripoli by sea. 



The Committee on African Climatology (President, Mr. E. 

 G. Ravenstein ; Secretary, Mr. H. N. Uickson) presented a 

 full and .satisfactory report, giving abstracts from twelve stations 

 in tropical Africa. Li recognition of the useful work done by 

 this Committee, it was reappointed with a small grant. 



Next to Africa the Arctic regions naturally commanded a 

 large share of 1 he attention of the .Section. Preliminary accounts 

 of three expeditions were given. Mr. J. Scott Keltie, who had 

 just returned from taking part in the Norwegian welcome to 

 Dr. Nansen, described his impressions of the explorer and his 

 companions, gave an outline of the work they had done, laying 

 special stress on Prof. Mohn's high estimate of the value of the 

 meteorological and magnetic observations, and announced that 

 Dr. Nanj^en would probably visit this country in November 

 in order to give a full account of his great journey before the 

 Royal Geographical Society. Mr. Montefiore Brice gave an 

 interesting report on the progress of the Jackson- Harmsworth 

 expedition, and showed by the lantern a number of photographs 

 taken in F"ranz Josef Land, including some of the arrival of Dr. 

 Nansen at Mr. Jackson's headquarters. He stated that next 

 year it was probable that the expedition would be reinforced by 

 two ships to push forward exploration in the sea north of Franz 

 Josef Land. Sir W. Martin Conway described his experiences 

 in crossing the interior of Spitzbergen last summer, the .soft 

 condition of the snow and the marshy character of the land 

 having interposed obstacles which could not have been foreseen 

 from the observations of earlier travellers. Mr. Frederick W. 

 Howell and Dr. K. Grossman exhibited a number of striking 

 pictures of the scenery of little-known parts of Iceland, the 

 former dealing mainly with glacial, the latter with volcanic 

 forms. 



Other de.scriptive papers, in all cases admirably illustrated, 

 were contributed by Mr. W. A. L. Fletcher, on his journey 

 across Tibet from north to south, on which he accompanied 

 Mr. and Mr.s. St. (Jeorge Littledale ; by Mr. H. W. Cave, on 

 the ruined cities of Ceylon ; and by Mr. A. E. FitzGerald, on 

 his crossing of the Southern Alps in New Zealan<l. Mr. 

 FitzGerald announced that he was about to a lead a party to the 

 Southern Andes, where he hoped to make the first ascent of 

 Aconcagua. 



Sir James Grant gave an eloquent address on the gold dis- 

 coveries in Canada, and Mr. E. Odium, of \'ancouver, described 

 the contested territories on the borderland of British Columbia 

 and Alaska. These papers attracted the greater attention on 



NO. 1407, VOL. 54] 



account of the apjjroaching visit of the British Association to 

 Toronto. Mr. Ralph Richardson initiated a short discu.ssion on 

 the boundary lines in British Guiana, attributed to Sir Robert 

 .Schomburgk. 



The geogra])hy of the BritLsh Islands was not lost sight of at 

 the meeting. The Rev. W. K. R. Bedford described some old 

 tapestry maps of parts of England, woven at Weston in the 

 last quarter of the sixteenth century, nnw preserved in the 

 Bodleian Library at Oxford, and in the Chapter-house at York. 

 They are on the scale of about four inches to one mile, ami 

 show some features which do not appear on the maps in con- 

 temporary atlases. Dr. H. R. Mill called attention to his 

 .scheme for a geographical memoir to accompany the maps of 

 the Ordnance Survey, on a specimen of which he is now at 

 work. Dr. Gulliver, of Harvard, gave an interesting discussion 

 of the coast-forms of Roniney Marsh, dwelling on the origin of the 

 cuspate foreland of Dungeness, and pointing out the importance 

 of treating such problems according to the genetic cycle. Mr. 

 B. V. Darbishire showed by a series of maps of the South Wales 

 coal-field, how the physical structure of the country controlled 

 the distribution of population, and the construction of lines ol 

 communication. 



There were several papers dealing with physical geography. 

 Mr. John Coles gave a demonstration of two methods of photo- 

 graphic .surveying, exhibiting the cameras used for each. He 

 expressed his conviction that photograjihic methods were bound 

 to take a very important place indeed in the surveys of the 

 immediate future. Prof. J. Milne discussed earthquakes and 

 sea-waves, with special reference to recent occurrences in Japan ; 

 and Mr. H. N. Dickson gave a short account of the work which 

 he hasin progress on the temperature and composition of the water 

 of the North .\tkntic. Mr. A.J. Herbert.sDii exhibited .some of 

 a series of maps of the mean monthly distribution of rainfall for 

 the world, which he is at present engaged in compiling, in col- 

 laboration with Dr. Buchan. They present the facts of the 

 distribution of rainfall for the first lime in a form admitting ol 

 the study of seasonal variations. 



Mr. X'aughan Cornish contributed one of the most valuable 

 and original papers read to the Section, in the form of a 

 practical study of the formation and distribution of sand- 

 dunes. He said that in the sorting of materials by wind 

 the coar.ser gravel is left on stony deserts or sea-beaches, 

 the sand is heaped up in dune tracts, and the dust (consist- 

 ing largely of friable materials which have been reduced 

 to powder in the dune district it.self) forms widely-scattered 

 deposits beyond the limits of the dune district. Three jjrincipal 

 factors operate in dune tracts, viz. (i) the wind, (2) the eddy in 

 the lee of each obstacle, (3) gravity. The wind drifts the fine 

 and the coarse sand. The upward niotiim of the eddy lifts the 

 fine sand, and, co-operating with the wind, .sends it flying from 

 the crest of the dune. The backward motion of the eddy 

 arrests the forward drift of the coarser sand, and thus co-operates 

 with the wind to build the permanent structure of the dune. 

 Gravity reduces to the angle of rest any slo]ies which have been 

 forced to a steeper pitch either by wind ureddy; hence in a 

 group of dunes the amplitude cannot be greater than (about) 

 one-third of the wave length. This limit is most nearly ap- 

 proached, owing to an action which the author explained, when 

 the wind blows alternately from opposite quarters. Gravity also 

 acts upon the sand which flies from the crests, causing it to fall 

 across the stream lines of the air. To the varying density of the 

 sand-shower is due the varying angle of the w indward slope of 

 dunes. When there is no sand-shower the w indward becomes 

 as steep as the leeward slope. When the dune tract is all deep 

 sand the lower part of the eddy gouges out the trough, and, when 

 the .sand-shower fails, the wind by drifting and the eddy by 

 gouging, form isolated hills upon a hard bed. In a district of 

 deep sand, negative dunes ("Suljcs") may be formed. The 

 encroachment of a dune tract being due not only to the march 

 of the dunes (by drifting), but also to the formation of new dunes 

 to leeward from material supplied by the sand-shower, it follows 

 that there is both a " group velocity " and a " wave velocity" of 

 dunes. .Since the wave velocity decreases as the amplitude 

 increases, a sufficiently large dune is a stationary hill, even 

 though composed of loose sand throughout. Where material is 

 accumulated by the action of tidal currents, forms homologous 

 with the ground plan of dunes are shown upon the chart.s. The 

 vertical contours and the movements of subaqueous sand dunes are 

 conditioned by the diflerent tactics of sand-shower and sand-drift. 



The educational aspect of geography was brought forward on 



