1885.] 
Sanitary Agency of Light. 
597 
7 Yu may Sa L y that without clarification and decolon- 
isation there can be no thorough purification ! 
but we have now to call to mind the faCt that certain 
systems of sewage treatment-systems which have been 
loudly vaunted and which it has even been sought to force 
S r h \r° n t0 the 6Xclusi0n of a11 otherUaauaHy 
Withdraw the sevvage and waste waters from the aftion of 
Ii^ht. Take, for instance, broad irrigation.” The sewage 
conveyed from the town down to the irrigation farm, rapidly 
finds its way into the earth, where it is protected from the 
sun We may grant that the lifeless organic matter, present 
in the sewage in suspension or solution, will be to a great 
extent oxidised or burnt up. But there is no evidence that 
tins late awaits the living micro-organisms of the sewage. 
r r \ th /o C ° ntrary ’ there is P ositive evidence — as in the cele- 
brated Swiss case— that they may and do emerge from the 
earth without being attenuated. Further, in a well- 
airanged precipitation system, the water — rendered trans- 
parent by the removal of colouring-matter and suspended 
impurities— is exposed for some time to the light in the 
precipitation- tanks, and after that it is often conveyed in 
open shallow channels for some distance, having the fullest 
opportunity of insolation. S 
It is, perhaps, rather a misfortune that other considerations 
compel us to convey sewage from the places of its production 
in covered channels, and thus seclude it from the beneficent 
action of light. 
lliere are quite other spheres where the ignorance of the 
piesent day wilfully excludes the sun. Suppose the very 
common case of a family dwelling in London, or in any 
other of our large towns, and going off in August to the 
sea-side for a fortnight, or perhaps for a longer time. One 
of their most pressing cares on setting off is to close every 
shutter and blind in the entire house from basement to attic. 
That this step should be taken with windows accessible 
from the street is not to be wondered at, but why rooms on 
the second floor and the attics should thus be consigned to 
darkness for such a lapse of time it is hard to understand. 
Perhaps to leave any opening for the light to enter would be* 
a social sin for which Mrs. Grundy has in reserve heavy 
penalties. We lift up our eyes, and, looking from our 
library window across two series of suburban gardens in 
which 
“ Life dies, death lives, and Nature breeds 
Perverse all monstrous, all detested things,” 
we see the back of a house which has thus been closed for 
