Irrigation. 
411 
chalk  if  it  be  soft  enough,  and  so  save  all  hand-work  and  car- 
riage. I have  seen  this  succeed  on  the  Surrey  hills. 
§ 9.  Irrigation. 
The  formation  and  use  of  catch-meadows  have  been  lately 
described  in  this  Journal.*  They  cost  about  ol.  an  acre  to  form, 
while  farmers  say  that  they  double  the  produce;  and  their  for- 
mation may,  therefore,  reasonably  be  set  down  as  yielding  a profit 
of  from  30  to  50  per  cent.  No  other  agricultural  investment 
can  be  compared  with  them  for  profit  and  convenience.  They 
belong  specially  to  the  western  or  rainy  sides  of  Great  Britain 
and  of  Ireland,  where  the  mild  winters  favour  the  growth  of 
grass,  and  they  are  at  home  on  the  mountain  sides  which  rise  on 
those  coasts.  But  though  born  on  the  glen-side  they  have  spread 
over  the  flats,  and  I have  found  them  invaluable  on  the  dry  side 
of  England  for  summer  use  also  during  long  drought.  Some- 
times, too,  gutters  may  be  cut  very  cheaply,  say  for  1Z.  an  acre, 
to  distribute  the  occasional  floods  of  rivers — an  improvement 
which  may  be  equal  to  a dressing  of  dung.  Summer  irrigation  has 
a tendency  in  some  places  to  rot  sheep,  but  it  has  not  done  so  yet 
here,  and  the  water  is  laid  during  summer  on  the  Duke  of  Port- 
land’s famous  meadows  at  Clipstone.  I have  obtained  from  a 
friend  for  the  present  Journal  an  account  of  the  water-meadows 
in  Switzerland.  There,  as  here,  the  growth  of  watercresses  and 
excellence  of  the  fish  are  the  proofs  of  water  fit  for  this  purpose. 
But  they  have  a third  proof — the  power  of  dissolving  soap.  This 
sets  at  rest  the  question  whether  water  must  be  hard  for  irrigation  ; 
since  every  washerwoman  knows  that  hard  water  contains  lime, 
and  curdles  her  soap.  The  peculiar  softness  of  feel  as  a test  of 
good  water  leads  me  to  believe  in  a new  cause  of  its  mysterious 
action,  not  exclusive  of  the  old  causes,  but  additional  to  them,  for 
icinter  irrigation  is  a complex  phenomenon.  In  speaking  of 
ammonia  brought  from  the  air  by  rain,  Liebig  says,f 
“ The  sensation  produced  upon  moistening  the  hand  with  rain-water, 
so  different  from  that  produced  by  pure  distilled  water,  and  to  which  the 
term  softness  is  vulgarly  applied,  is  also  due  to  the  carbonate  of  ammonia 
contained  in  the  former.” 
He  further  tells  us  that  Hiinefeld  has  proved  all  the  springs  in 
Greifswalde  and  three  other  places  to  contain  carbonate  and 
nitrite  of  ammonia.  It  appears  to  me  a legitimate  inference  that 
our  own  soft  and  warm  springs  issuing  from  the  depths  of  the 
earth,  fertilize  our  meadows  by  bringing  with  them  ammonia,  the 
result  perhaps  partly  of  ancient  volcanic  action,  partly  acquired 
by  filtration  through  the  upper  soil,  for  in  soil  too,  even  unculti- 
* On  Catch-Meadows,  Journal,  x.  462. 
f Liebig’s  Agricultural  Chemistry,  4th  edit.  p.  46. 
