136 J. ASHBURTON THOMPSON, 
their heads off, and are a source of stinks and difficulties, and of 
danger to health too. I have no doubt at all that the separate 
system is the most sensible, the most economical, and all ronnd 
the best way of sewering towns. That is a sweeping statement ; 
but since it has been abundantly demonstrated in actual practice 
Ido not see how anyone can doubt it, and in a new country 
where new towns are springing up every day I do not hesitate to 
express it. 
Are there then no difficulties in the way? Is the whole matter — 
quite as simple as I have represented it to be? In new towns it 
is ; in large and long-established cities it is not. But it is not 
with old cities that [am now concerned, although I shall have to 
mention them presently. We are considering new towns built 
without overcrowding; and my suggestion is that for them the 
separate system is not only the best, but that it is the only one 
possible when means are small. You know what difficulty I 
have in mind in making those remarks. It is the alleged difficulty 
of excluding all surface waters from sewers. Now as to that I 
wish to say quite clearly that I decline to regard surface waters 
as sewage. My reason is simple. It is mainly this: However 
foul rainfall may become after sweeping over a town area, yet it 
so sweeps but intermittently— such storms do not happen every 
week, nor even very frequently ; and then, foul as the first flow 
may be, there are but few such storms that do not last long enough 
for the later flow to be comparatively clean, and such as carries 
along with it little besides mineral matters. That is my main 
reason. But, after all, the foulness of such flows is relative to 
foulness of surface. Under reasonable scavenage the first flow 
should not be excessively foul, and should be very soon followed 
by the clean flow which would effectually cleanse the drains by 
which it should pass. On the other hand, if scavenging is so ill 
done that this is not the case, then admission of an intermittent 
foul-surface-flow to sewers will not at all lessen the illness that 
the foul surface caused when there was no rain to scavenge it ; 
or to take another. view, if the general surface is usually foul, then 
