Where the lift is very little, shadoofs and sakiehs are replaced by instruments called Natalis and Archimedean screws; but, naturally, since the introduction of perennial irrigation has so increased the area to be watered by lift, machinery has had to be called in, and most of the work is done by pumps worked by steam. Each large land-owner has his own pump and engine, which can be moved from place to place, and are also hired out to the smaller men. On very large estates stationary engines have been erected, which, of course, are able to raise a much larger amount of water; but as a rule the machinery employed is a portable eight-horse-power engine and an eight-inch centrifugal pump. How different is all this from the lot of the agriculturist in other lands! For him there is no digging or maintenance of canals; no apparatus of regulators, dams, sluice-gates, siphons, and drains; no painful lifting of the water by pumps and engines, shadoofs, and sakiehs. The rain falls upon his fields from heaven without any effort of his. He looks to Providence to regulate his supply; the Egyptian looks to a Government department. But the Egyptian, as a compensation for his extra labour, has the advantage of greater certainty. He knows the sun will shine. The rise and fall of the Nile, variable as it is, can be foretold with greater exactness than that of any other river—with far greater exactness than the duration of the rainy season in any country in the world. Nature indeed made his task simple in the extreme, if he had been content with one crop a year. Every year the flood thoroughly washed the land, and kept it free from injurious salts; it also covered them with a deposit of mud, which relieved him from the necessity of dressing and manuring the exhausted soil. The Nile silt, though singularly rich in potash, the principal food of leguminous plants, like peas, beans, and clover, is, however, very poor in the nitrates on which cereals depend. But the Egyptian clover, called bersine, has the property of secreting nitrates from the air, and depositing them in the soil to an extraordinary extent, so that the land was able to bear crops of clover and cereals in rotation to an unlimited extent without any manuring. The desire to grow rich by crops like cotton and sugar, and by forcing the land to double its output, has changed all this. Not only has the summer supply of water become of the utmost importance, but the soil has to be constantly refreshed with manures. The question of manures is, indeed, only second, under perennial irrigation, to the question of water.