46 



NATURE 



[September io, 1914 



been converted into forest land, planted mainly with 

 maritime pines. 



What, again, will irrigation have to say to the 

 deserts? Irrigation, whether from underground or 

 from overground waters, has already changed the face 

 of the earth, and as the years go on, as knowledge 

 grows and wisdom, must inevitably change it more 

 and more. I read of underground waters in the Kala- 

 hari. I read of them too in the Libyan Desert. In 

 the Geographical Journal for 1902 it is stated that 

 at that date nearly 22,000 square miles in the Algerian 

 Sahara had been reclaimed with water from artesian 

 wells. What artesian and sub-artesian water has done 

 for Australia you all know. If it is not so much avail- 

 able for agricultural purposes, it has enabled flocks 

 and herds to live and thrive in what would be other- 

 wise arid areas. Prof. J. W. Gregory, Mr. Gibbons 

 Cox, and others have written on this subject with 

 expert knowledge ; evidence has been collected and 

 published by the Dominions Royal Commission, but I 

 must leave to more learned and more controversial 

 men than I am to discuss whether the supplies are 

 plutonic or meteoric, and how far in this matter you 

 are living on your capital. 



If we turn to irrigation from overground waters, I 

 hesitate to take illustrations from Australia, because 

 my theme is the blotting out of the desert, and most 

 of the Australian lands which are being irrigated from 

 rivers, and made scenes of closer settlement, w^ould be 

 libelled if classed as desert. Mr. Elwood Mead told 

 the Royal Commission that the State irrigation works 

 in Victoria, already completed or in process of con- 

 struction, can irrigate more than 600 square miles, 

 and that, if the whole water supply of the State were 

 utilised, more like 6000 square miles might be irri- 

 gated. The Burrinjuck scheme in New South Wales 

 will irrigate in the first instance not far short of 500 

 square miles, blit may eventually be made available 

 for six times that area. If we turn to irrigation 

 works in India, it appears from the second edition of 

 Mr. Buckley's work on the subject, published in 1905, 

 that one^ canal system alone, that of the Chenab in 

 the Panjab, had, to quote his words, turned " some 

 two million acres of wilderness (more than 3000 square 

 miles) into sheets of luxuriant crops." " Before the 

 construction of the canal," he writes, " it was almost 

 entirely waste, with an extremely small population, 

 which was mostly nomad. Some portion of the 

 country was wooded with jungle trees, some was 

 covered with small scrub camel thorn, and large tracts 

 were absolutely bare, producing only on occasions a 

 brilliant mirage of unbounded sheets of fictitious 

 water." The Chenab irrigation works have provided 

 for more than a million of human beings ; and, taking 

 the whole of India, the Irrigation Commission of 

 1 90 1-3 estimated that the amount of irrigated land at 

 that date was 68,750 square miles ; in other words, 

 a considerably larger area than England and Wales. 

 Sir William Willcocks is now reclaiming the delta of 

 the Euphrates and Tigris. The area is given as nearly 

 19,000 square miles, and it is described as about two- 

 thirds desert and one-third freshwater swamp. More 

 than 4000 square miles of the Gezireh Plain, between 

 the Blue and the White Nile, are about to be re- 

 claimed, mainly for cotton cultivation, by constructing 

 a dam on the Blue Nile at Sennaar and cutting a 

 canal 100 miles long which, if I understand right, will 

 join the White Nile, thirty miles south of Khartoum. 



With the advance of science, with the growing 

 pressure of population on the surface of the earth, 

 forcing on reclamation as a necessity for life, is it too 

 much to contemplate that human agency in the 

 coming time will largely obliterate the deserts which 

 now appear on our maps? It is for the young peoples 

 of the British Empire to take a lead in — to quote a 



NO. 2341, VOL. 94] 



phrase from Lord Durham's great report — "the war 

 with the wilderness, and the great feat of carrying 

 water for 350 miles to Kalgoorlie, in the very heart 

 of the wilderness, shows that Australians are second 

 to none in the ranks of this war. 



It is a commonplace that rivers do not make good 

 boundaries because they are easy to cross by boat or 

 bridge. Pascal says of them that they are "des 

 chemins qui marchent " (roads that move), and we 

 have seen how these roads have been and are being 

 improved by man. " Rivers unite," says Miss Semple ; 

 and again, " Rivers may serve as political lines of 

 demarcation, and therefore fix political frontiers, but 

 they can never take the place of natural boundaries." 

 All the same, in old times at any rate, rivers were very 

 appreciable dividing-lines, and when you get back to 

 something like barbarism, that is to say in time of 

 war, it is realised how powerful a barrier is a river. 

 Taking, then, rivers as in some sort natural boun- 

 daries, or treating them only as political boundaries, 

 the point which I wish to emphasise is that they are 

 becoming boundaries which, with modern scientific 

 appliances, may be shifted at the will of man. In the 

 days to come the diversion of rivers may become the 

 diversion of a new race of despotic rulers with in- 

 finitely greater power to carry out their will or their 

 whim than the Pharaohs possessed when they built the 

 Pyramids. You in Australia know how thorny a ques- 

 tion is that of the control of the Murray and its 

 tributaries. There are Waterways Conventions be- 

 tween Canada and the United States. Security for 

 the head-waters of the Nile was, and is, a prime neces- 

 sity for the Sudan and Egypt. The Euphrates is 

 being turned from one channel into another. What 

 infinite possibilities of political and geographical com- 

 plications does man's growing control over the flow of 

 rivers present ! 



Thus I have given you four kinds of barriers or 

 divisions set by Nature upon the face of the earth — 

 mountains, forests, deserts, rivers. The first, the 

 mountains, man cannot remove, but he can and he 

 does go through them to save the trouble and difficulty 

 of going over them. The second, the forests, he has 

 largely cleared away altogether. The third, the 

 deserts, he is beginning to treat like the forests. The 

 fourth, the rivers, he is beginning to shift when it 

 suits his purpose and to regulate their flow at will. 



I turn to climate. Climates are hot or cold, wet or 

 dry, healthy or unhealthy. Here our old friends the 

 trees have much to say. Climates beyond dispute 

 become at once hotter and colder when trees have 

 been cut down and the face of the earth has been 

 laid bare ; they become dryer or moister according as 

 trees are destroyed or trees are planted and hold the 

 moisture; the cutting and planting of timber affects 

 either one way or the other the health of a district. 

 The tilling of the soil modifies the climate. This has 

 been the case, according to general opinion, in the 

 North-West of Canada, though I have not been able 

 to secure any official statistics on the subject. In 

 winter time broken or ploughed land does not hold 

 the snow and ice to the same extent as the unbroken 

 surface of the prairie ; on the other hand, it is more 

 retentive at once of moisture and of the rays of the 

 sun. The result is that the wheat zone has moved 

 further north, and that the intervention of man has, 

 at any rate for agricultural purposes, made the climate 

 of the great Canadian North-West perceptibly more 

 favourable than it was. In Lord Strathcona's view, 

 there was some change even before the settlers came 

 in, as soon as the rails and telegraph lines of the 

 Canadian Pacific Railway were laid. He told me that 

 in carrying the line across a desert belt it was found 

 that, within measurable distance of the rail and the 

 telegraph line, there was a distinct increase of dew 



