470 Toicn Sewacje. 



progress ; tliough scarcely more than a generation old, it lias 

 already increased our domestic comfort, and our immunity from 

 zymotic disease, as statistics abundantly show. If, so far, it 

 has sacrificed the manure and injured our rivers, there is more 

 hope for amendment in this inodern system than in that which 

 the lapse of ages has failed to rectify. Practically, therefore, 

 our problem assumes this shape — how shall we deal with dilute 

 town sewage, the foul stream which flows through the under- 

 ground veins and arteries of our great cities ? 



Portable Manuee made from Sewage. 



Many plans have been proposed for the separation of the 

 valuable constituents from sewage-water. Some of these have 

 succeeded in separating the whole of the insoluble or sedi- 

 mentary matter, and even some small portion of the soluble con- 

 stituents, leaving the fluid to a great extent, or at any rate tem- 

 porarily, purified ; none have succeeded in either adequate or 

 permanent purification, or in the separation of the more valuable 

 manurial matters, and the production of a concentrated^ dry, 

 easily transportable manure, which may be redistributed over 

 the extended area to the variety of crops from which its 

 ingredients were first derived ; moreover the great solubility of 

 some of the more precious constituents precludes the hope of 

 so desirable a consummation. 



We have therefore to dispose of the sewage in a dilute form, 

 and these questions arise : — 



What is its composition and value ? 



What is the amount furnished by a given population ? 



To what soils and crops is it most applicable ? 



Composition and theoretic Value of Town Sewage, 



Widely different will be the estimates of value formed by 

 theorists who overlook all but the fact that so much of nitrogen, 

 phosphoric acid, &c., is to be found in sewage, and those of 

 practical men who have tried to grapple with the unwieldy body 

 in which these substances are diffused. 



For arriving at its average composition, two methods have been 

 adopted. The first, by taking samples of sewage, determining its 

 composition by analysis, and then adopting such estimates as were 

 to be had, as to the amount of sewage available Avithin a given 

 time. The second, by calculating the amount of faeces and urine 

 (or their constituents) for a given population of different sexes 

 and ages, with such adjustment for loss or for the addition of 

 extraneous fertilisers as circumstances suggested. 



