SEWAGE. 267 



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 re- 

 turn 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 seri- 

 ously augmented by the fact that cities, and all con- 

 siderable 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 vil- 

 lages 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. 



Yet the problem, though difficult, must be solved, 

 or our great cities will be destroyed by their own 

 physical impurities. The growth and expansion of 

 cities, throughout the present century, have been 

 wholly beyond precedent ; and thus the difficulty of 

 making a satisfactory disposition of their offal has 

 been fearfully augmented. The sewerage of our 

 streets and houses modifies the problem, but does not 



