The great art of irrigation was studied and used with splendid success by the ancient nations of the near East. They converted deserts into gardens, and their work was an act of compensation and restitution to be set off against the destructive operations of more barbarous men. But they, too, long ago were themselves destroyed by conquering hordes of more ignorant but more war-like men, and their irrigation works and the whole art of irrigation perished with them. One of the absolutely necessary works to be carried out by civilised man, when he has ceased to build engines of war and destruction, is the irrigation of the great waterless territories of the globe. A little home-work of the kind has been carried on in Italy regularly year by year since the days of Leonardo da Vinci, and our Indian Government is slowly copying the Italian example. In Egypt we have built the great dam of Assouan, whilst in Mesopotamia it is proposed to re-establish the irrigation system by which it once was made rich and fertile. But, as has lately been maintained by Mr. Rose Smith in his book, "The Growth of Nations," the vast possibilities of irrigation have not yet been realised by the business men of the modern world. Millions of acres in the warmer regions of the earth now unproductive can be made to yield food to mankind and rich pecuniary profits to the capitalists who shall introduce modern engineering methods and a scientific system of irrigation into those areas. The whole problem of the increase of the more civilised races and the necessary accompanying increase of food-production depends for its solution on the speedy introduction of irrigation methods into what are now the great unproductive deserts of the world. CHAPTER XXV THE EXTINCTION OF THE BISON AND OF WHALES