But  it  Would  be  wrong  to  rely  on  the  disinfecting  properties
of  sandy  and  gravelly  sods.  They  have  not  proved  their  capa-
bility of  decomposing  nitrogenous  organic  matter,  or  of  fixmg
its  elemetits  in  vegetable  growth.  They  cannot,  therefore,  bd
depended  on  for  the  completion  of  that  marvellous  cycle  of  life,
that  adjustment  of  the  balance  of  organic  nature,  which  Dumas
and  Boussingault  long  ago  demonstrated  as  essential  to  the
existence  of  plants  and  animals — that  "  eternal  round  in  which
death  is  quickened  and  life  appears,  but  in  which  matter  merely
changes  its  place  and  its  form."

From  the  evidence  already  in  our  possession,  and  on  review-
ing many  conflictiug  statements,  it  may,  I  think,  be  fairly
inferred,  that,  in  the  use  of  fluid  sewage  for  land  irrigation,  the
following  sanitary  conditions  should  be  observed.
An  extent  of  land  surface  should  be  obtained,  which  shall  be
sufficient,  Under  engineering  direction  and  proper  precautions,
to  absorb  the  whole  of  the  fluid  in  dry  weather;  sufficient
to  decompose  and  fix  its  organic  constituents;  sufficient^
again,  to  prevent  atmospheric  pollution;  sufficient,  also,  to
admit  of  long  intervals  between  the  periodical  applications  of
the  fluid  to  each  portion  of  the  surface ;  and,  therefore,  «nfficiettt
to  promote  a  succession  of  crops,  roots  and  cereals,  so  that  we
may  hear  of  something  better,  on  good  soils,  than  Italian  rye-
grass.
To  secure  the  fulfilment  of  these  conditions,  and  on  physio-
logical grounds  generally,  though  perhaps  not  in  accordance
with  eminent  engineering  authority,  I  suggest  that  not  less
than  an  acre  of  clay  or  loam  be  secured  for  every  thirty  or
forty  of  town  population.
