47 
in  its  Effect  on  Cultivation. 
counties  sheltered  by  the  Welsh  mountains,  where  the  soil  is  rich, 
the  surface  undulating,  and  the  summer  warm,  and  where  the 
destroying  east  wind  has  less  effect  than  in  any  other  part  of 
England.  For  these  reasons  the  counties  of  Hereford,  Gloucester, 
and  Worcester  are  celebrated  for  their  orchards,  and  make  large 
quantities  of  cider  and  perry.  Shelter  from  blighting  winds,  a 
situation  above  the  cold  fogs  of  the  valley  and  the  reach  of  hoar- 
frost, are  the  requisites  of  climate  which  should  be  sought. 
106.  Effect  of  Elevation  on  Agricultural  Produce. — The  effect 
of  elevation  on  temperature  has  been  already  examined  (16),  and 
the  result  of  careful  observations  gives  a decrease  of  1°  of  heat 
for  every  270  feet  of  altitude.  Lands  at  an  ordinary  level  have 
not  a greater  summer  heat  than  is  desirable  for  grain-crops,  and 
this  rapid  diminution  of  temperature  limits  the  superior  kinds  of 
corn  to  a lower  elevation  than  is  generally  supposed.  There  is 
also  great  irregularity  in  the  ripening  of  corn  on  high  lands. 
The  state  of  the  soil  and  local  climate  produce  different  effects  at 
the  same  height.  Some  late  soils  in  the  west  have  had  an  earlier 
harvest  by  a week  or  ten  days,  by  a liberal  application  of  shell- 
sand  from  the  coast.  In  dry  warm  years  the  difference  is  but 
small  between  the  time  of  harvest  on  elevated  and  low  lands  ; but 
in  wet  years,  on  the  high  moors  of  the  north  of  England  and 
Scotland,  this  time  is  extended  to  six  weeks,  or  even  two  months. 
From  this  cause  very  contradictory  statements  and  opinions  are 
afloat  on  this  subject.  In  consequence  of  the  drier  air  of  the 
east  and  middle  of  England,  the  cultivation  of  corn  can  be  car- 
ried successfully  to  a greater  height  there,  than  on  the  wet  westei'n 
coast. 
In  the  west  of  England,  wheat  is  grown  with  variable  and  often 
doubtful  success  to  a height  of  600  feet.  Oats  answer  well  at 
1000  feet,  the  harvest  being  from  ten  days  to  a fortnight  later 
than  on  the  low  lands. 
In  Wales,  on  the  sides  of  Cader  Idris,  bad  crops  of  wheat  are 
grown  at  700  feet.  On  the  great  English  plain  there  are  few,  if 
any,  places  where  the  climate  prohibits  the  growth  of  corn.  On 
the  wolds  of  Lincoln  and  York,  excellent  barley  is  grown.  The 
general  height  of  the  Cotswold  Hills,  omitting  the  highest  points, 
is  from  500  to  600  feet ; and  it  is  doubtful  whether  wheat  can  be 
grown  with  that  advantage  which  justifies  the  exclusion  of  another 
crop.  The  middle  part  of  the  Yorkshire  moors  is  about  1000 
feet  high,  oats  and  bere  are  the  principal  crops  ; wheat  is 
seldom  sown  higher  than  800  feet,  and  is  then  precarious.  The 
harvest  on  the  moors  is  a month  later  than  on  the  low  lands. 
With  respect  to  Scotland,  I have  been  favoured  on  this  subject 
with  a letter  from  the  Rev.  William  Dunbar,  whose  meteoro- 
logical observations  are  well  known.  It  contains  such  valuable 
