and that it will cost thereafter $1 per acre to apply it, I maintain that it is richly worth having, and that nearly every farm product can be grown cheaper by its help than on lands where irrigation is presumed unnecessary. There are not many acres laid down to grass in New-England, whether for hay or pasture, that would not have justified an outlay of $10 per acre to secure their thorough irrigation simply for this year alone. XLV. SEWAGE. The great empires of antiquity were doomed to certain decay and dissolution by a radical vice inherent in their political and social constitution. Power rapidly built up a great capital, whereto population was attracted from every quarter; and that capital became a focus of luxury and consumption. Grain, Meat, and Vegetables--the fat of the land and the spoils of the sea--were constantly absorbed by it in enormous quantities; while nothing, or, at best, very little, was returned therefrom to the continually exhausted and impoverished soil. Thus, a few ages, or at most a few centuries, sufficed to divest a vast surrounding district, first, of its fertility, ultimately of its capacity for production. And so Nineveh, Thebes, Babylon, successively ceased to be capitals, and became ruins amid deserts. Rome impoverished Italy south of the Apennines; then Sicily; and, at last, Egypt: her sceptre finally departing, because her millions could no longer be fed without dispersion. That some means must be devised whereby to return to the soil those elements which the removal of crop after crop inevitably exhausts, is a truth which has but recently begun to be clearly understood. Unluckily, the difficulty of such restoration is seriously augmented by the fact that cities, and all considerable aggregations of human beings, tend strongly in our day to locations by the sea-side, in valleys, and by the margins of rivers. Anciently, cities and villages were often built on hill-tops, or at considerable elevations, because foes could be excluded or repelled from such locations more surely, and with smaller force, than elsewhere. From such elevations, it need not have been difficult to diffuse, by means of water, all that could be gladly spared which would aid to fertilize the adjacent farms and gardens. A kindred distribution of the exuviae of our modern cities is a far more difficult and costly undertaking, and involves bold and skillful engineering.