SEWERAGE OF A SEASIDE TOWN. 769 



good outfall at a point wliere there are sets of currents that 

 carry everything out to sea, advantage may be taken of such 

 a eircunistanee to avoid all expense of sewage treatment bv 

 discharging it directly into the water. If, again, the town be 

 on a beach, or on a tidal river, wliere the ebb and tiow of 

 tide are such as to retain for a time, floating up and down, 

 the matters thrown into it, with a tendency probablv to 

 deposit them upon the shore, it is clear that in most cases it 

 would not be advisable to discharge sewage directly into the 

 water without some treatment that would prevent nuisance 

 arising therein from the action of the tide, and, ])articularly, 

 that would prevent the deposit of noxious matters on the 

 beaches. It is equally clear also that, as the water into which 

 the discharge takes place, being salt, cannot be used as a 

 source of supply for domestic consumption, the treatment of 

 the sewage, while it should ert'ect the ])reventive measures 

 just referred to, need not be of the nature necessary to secure 

 the chemical purity that should be required in the case of the 

 inland town and the fresh-water river. As most of our large 

 colonial cities have arms of the sea or tidal rivers as the 

 natural outlets of their sewage, I propose, as a matter of 

 practical hygiene, to discuss the system of sewerage to be 

 recommended for their adoption, and to do so in the light of 

 comparatively recent developments of sanitary science as 

 applied to such Avork. 



As I have ajiproached my subject from the consideration 

 of the dominant circumstance of outfall as affectins," the 

 adoption of one or other of vai'ious systems of sewerage, I 

 shall begin by considering sewage disposal — that is, the work 

 done at the outfall — and afterwards take up the matter of 

 sewage collection. It may be thought by some that this will 

 be working backwards, as you must collect your sewage 

 before you can dispose of it ; but, on due thought, it will be 

 found that though sewage collection has only a very limited 

 bearing upon its disposal, the method of its disposal may 

 have a very great influence upon most of the details even of 

 the system of its collection — that is to say, upon the details 

 of the construction of the sewers. 



This disposal is, as above described, based on the supposition 

 that the sewage is to be discharged into the sea or a tidal 

 river, and that, preparatory to that discharge, it is only 

 necessary to partially purify it. This partial purification 

 especially in the case of a comparatively large city situated 

 upon a comparatively small tidal river, should be sufficient, 



