(>54 TRANSACTIONS OF THE AMERICAS INSTITUTE. 



of the underground, and also that this water, in connection with that 

 especially provided for the purpose, is to act as a vehicle for carrying 

 the first mentioned substances. 



Two important theories were put forward in regard to the organic 

 matter that was to be allowed to enter the sewers. One was that this 

 matter would' be carried to such a distance before any decomposition 

 could take place, that no danger was to be anticipated in the vicinity 

 from whence it was taken. The other theory was, that should any 

 decomposition take place in the nitrogeneous compounds of the mass, 

 the oxygen of the water would cause such a rapid oxydation, that 

 instead of a deleterious gas escaping in the atmosphere, a harmless 

 salt would be formed, which would be carried away with the effluent 

 water. 



As a greater part of the advantages sought for, by means of sewers, 

 depends upon one or the other of these results being accomplished, 

 it is desirable to know what exparience has shown us, and in treating 

 upon this matter I shall refer to the critical investigations of 

 undoubted authorities. 



Undoubtedly the most perfect system of sewers that can be found 

 anywhere are in some of the cities of England ; and in no country 

 has there been so good an opportunity of observing their workings. 

 In London, over £30,000,000 were expended upon the sewers in 

 twenty years, from 1846 to 1866. 



Previous to the construction of the present large sewer in that city, 

 the sewers in use opened into the Thames, and their contents flowed 

 into the river, at various points along the city, similar to the manner 1 

 in which the sewers of New York discharge themselves ; and the 

 consequence was, that the Thames, along its whole course through 

 that city, had become a surging cess-pool. In order to do away with 

 this nuisance, a large sewer was built parallel with the river, and the 

 other sewers so arranged that their contents should flow into this 

 great sewer. This main sewer was extended about twelve miles 

 below the city, where its contents had to be pumped up to the surface 

 of the earth. It was proposed, in some manner, to utilize this sew- 

 age, but this was found afterward to be impracticable, and it was 

 allowed subsequently to flow off into the Thames. It was, however, 

 soon found that the tide carried this stuff back again to the city, and 

 then came the famous " Thames Pollution Act," which prohibited the 

 discharge of sewage into the Thames. Since then the solid parts of 

 a portion of the sewage are allowed to subside in large reservoirs, 

 constructed for that purpose ; and another portion is allowed to flow 



