SANITARY SEWERAGE. 535 



Tliese systems are of recent development, and have been 

 designed to enable the sanitary engineer to command gradients 

 to the sewers under all circumstances that will be suitable to the 

 quantity of sewage he has to deal with, irrespective of the natural 

 inclination of tlie surface. Thus, low-lying localities may, as 

 regards sanitation, be placed on an equal footing with the most 

 favoured localities. 



It has been the custom to look upon sewers as proper receptacles 

 for all manner of tilth which it may be found necessary to get rid 

 of. If sewers are to be sanitary, they must be treated in a 

 different manner to this. 



The dejecta of persons suffering from contagious diseases should 

 be disinfected before it is admitted into the sewers. Decomposing 

 and putrid matter should receive similar treatment. Offensive 

 water from processes of manufacture should be deodorized and 

 disinfected Ijefore being passed into the sewers. 



It may be found impossible to exclude matters full of contagion 

 in isolated cases of disease, but the drainage from hospitals should 

 most certainly be disinfected before being discharged into the 

 sewers. 



The principles affirming the necessity of ensuring the non- 

 pollution of sources or possible sources of water supply and the 

 non-pollution of the atmosphere, when the disposal of sewage 

 is under consideration, cannot be taken exception to, and their 

 realisation in practice depends largely upon the observance of 

 the preceding principles. 



When sewage is delivered in a fresh condition at the outfall in 

 regular quantities undiluted with rain water, its disposal on land 

 for irrigation purposes no longer presents the difficulties that are 

 met with iii those instances where the admixture of rain water 

 yields an unmanageable quantity. 



If the exclusion of the storm water be rigidly adhered to, the 

 reduction in bulk of the sewage will enable it to be disposed of 

 at will. No science advances alone. The mechanical engineer 

 assists the sanitaiy engineer and shows him how to accomplish his 

 desires. Already new possibilities in sanitary engineering, sewage 

 disposal, and sewerage economics present themselves, and the time 

 is at hand when it will be found expedient and profitable by 

 delivering sewage on to the land to restore to the soil those 

 fertilising matters originally taken from it. 



The realisation of a sanitary water carriage system of sewerage 

 depends upon the skill and judgment of the engineer, in the 

 practical application of the principles which have been enunciated 

 to the physical condition of the locality where a sewerage system 

 has to be constructed. 



