652 
Climate  of  the  British  Islands 
and  descending  to  the  level  of  the  sea  in  the  counties  of  Inver- 
ness and  Aberdeen,  in  Scotland.  In  summers  like  1826  and 
1846  this  may  extend  to  850  feet  in  the  south,  and  at  the  level  of 
the  sea  to  Sutherland;  and  in  bad  seasons,  as  1841,  be  limited 
in  the  south  to  400  feet  above  the  level  of  the  sea,  and  at  that  level 
to  the  counties  of  Fife  and  Stirling,  in  Scotland.  It  will  be  readily 
seen  from  what  has  been  stated,  especially  with  the  present  pros- 
pects of  farmers,  that  I would  not  advise  the  growth  of  wheat  at 
any  high  level ; and  if  from  the  middle  of  Great  Britain  north- 
wards any  place  be  elevated  200  feet  above  the  level  of  the  sea, 
unless  the  slope  be  favourable,  crops  of  far  greater  safety  and 
profit  may  be  cultivated  than  wheat  in  such  a situation.  When 
it  is  necessary  to  grow  wheat  towards  the  limit  of  its  growth, 
either  in  elevation  or  latitude,  salt  should  always  be  used  as  part 
of  the  manure.  This  my  father  has  proved,  during  a long  course 
of  years,  to  cause  it  to  ripen  on  an  average  fully  a iveek  before 
wheat  in  the  manure  for  which  salt  had  formed  no  part. 
Barley,  like  wheat,  is  a native  of  a warmer  climate  than  that  of 
the  British  Islands,  and  is  affected  by  difference  oi  climate  in  a 
similar  manner  with  wheat.  It  succeeds  best  in  the  same  spots 
as  wheat  with  respect  to  climate,  only  requiring  different  soil. 
In  places  where  the  climate  is  favourable  it  will  yield  two  crops 
during  the  year,  as  in  Spain  and  Italy.  It  can  be  perfected  in 
the  short  space  of  ninety  days ; hence  some  have  argued  erro- 
neously respecting  it,  and  have  accounted  it  a hardy  grain,  as  it 
will  grow  in  Lapland  as  far  north  as  70°.  But  from  what  I have 
previously  stated  as  to  the  heat  of  summer  in  places  having  a 
high  latitude,  it  will  be  found  to  owe  its  cultivation  there  not  to 
its  hardihood,  but  to  the  short  period  required  for  its  growth,  the 
heat  of  that  period  being  in  Lapland  often  greater  than  it  is  at  the 
same  time  in  some  parts  of  Scotland,  It  will  not  generally  per- 
fect its  seed  below  a temperature  of  56°,  but,  according  to  Hum- 
boldt, will  succeed  wherever  the  temperature  of  three  months 
exceeds  48^°.  The  south  and  south-eastern  parts  of  our  island 
are  the  best  fitted  for  its  growth  ; and  Norfolk  barley  has  been 
long  famed  for  its  excellence.  Barley  is  very  tender,  and  is  fre- 
quently destroyed  by  the  blasting  fogs  which  occur  during  the 
autumn  in  Scotland,  whilst  oats  and  other  grain  are  comparatively 
uninjured.  It  requires  much  silica  in  the  soil  when  it  is  culti- 
vated ; and  a deficiency  of  this  ingredient  in  the  soil,  or  a moist 
season,  cause  it  to  grow  with  a stalk  too  tender  to  support  itself, 
and  as  the  ear  fills  it  falls  to  the  ground,  and  is  comparatively 
valueless.  The  height  to  which  it  may  be  cultivated  with  suc- 
cess in  our  islands  extends  from  1000  feet  in  the  south  to  800 
feet  in  the  south-east  of  Scotland  and  600  feet  in  the  south-west, 
and  approaches  near  to  the  level  of  the  sea  in  the  north  of  the 
