436 TRANSACTIONS OF SECTION R. 
camel thorn, and large tracts were absolutely bare, producing only on occasions 
a brilliant mirage of unbounded sheets of fictitious water.’ The Chenab irriga- 
tion works have provided for more than a million of human beings; and, taking 
the whole of India, the Irrigation Commission of 1901-3 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 has 
been 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. Over 4000 square miles of the Gezireh Plain, 
between the Blue and the White Nile, are about to be reclaimed, mainly for 
cotton cultivation, by constructing a dam on the Blue Nile at Sennaar and 
cutting a canal 100 miles Jong 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 oblite- 
rate 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 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 boundaries, 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 infinitely 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 question is that of the control of the Murray and 
its tributaries. There are Waterways Conventions between Canada and the 
United States. Security for the head-waters of the Nile was, and is, a prime 
necessity for the Sudan and Egypt. The Euphrates is being turned from one 
channel into another. What infinite possibilities of political and geographical 
complications 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 climates. Climates are hot or cold, wet or dry, healthy or un- 
healthy. 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 drier 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 
