54 
On  the  Climate  of  the  British  Islands 
by  which  it  is  fitted  for  assimilation  is  slow  (perhaps  through  the 
deficiency  of  the  alkali),  and  the  general  experience  of  the  farmers 
is  against  the  growing  of  wheat  on  a grauwacke  soil  oftener  than 
once  in  five  years. 
On  inspecting  the  valuable  analyses  of  the  ashes  of  wheat  in  the 
7th  Volume  of  this  Society’s  Journal,  I observed  the  instructive 
fact,  that  the  perfection  of  the  grain  is  dependent  on  the  quantity 
of  potash  it  contains.  I have  extracted  the  following  examples 
of  Hopeton  wheat  as  illustrations:  — 
Lbs.  per 
Bushel. 
Description. 
Potash 
per  Cent. 
56 
Bad  .... 
26-9 
59 
Grain  good 
33-15 
60 

30-32 
64 
Rattier  thin 
32-05 
62 
Good  .... 
34-51 
63 
Good  .... 
36-43 
These  facts  show,  that  wheat  cannot  successfully  be  grown 
unless  the  soil  contains  an  adequate  supply  of  potash,  and  where 
this  crop  occurs  oftener  in  the  rotation  than  the  alkali  in  the 
soil  will  bear,  the  grain  must  ultimately  prove  defective  in 
quality. 
On  the  north  of  Cornwall,  at  Lambourne,  on  a grauwacke  soil, 
the  four-course  shift  was  strictly  adhered  to,  but  the  quality  of  the 
wheat  fell  off  so  much,  as  to  induce  some  modification  of  the 
system.  Wheat  is,  however,  grown  in  quick  succession,  on  a low 
lying  loamy  soil  near  Wadebridge. 
Red  clover  has  not  answered  well  in  the  West  of  late;  but 
rape  has  been  so  advantageously  raised,  and  forms  such  an 
excellent  preparation  for  wheat,  that  it  must  form  a part  of  any 
efficient  rotation  adapted  to  the  soil  and  climate.  For  these 
reasons  I am  of  opinion  that  the  general  introduction  of  the  four- 
course  system  would  not  be  successful  in  the  West.  On  low- 
lying  rich  loams,  here  and  there,  it  would  no  doubt  succeed ; but 
a rotation  which  combines  the  roots  and  fodder  of  the  four-course, 
with  such  an  alternation  of  grain  crops  in  which  wheat  forms  a 
less  prominent  part,  and  then  preceded  by  rape,  is  that  which, 
under  the  general  circumstances  of  soil  and  climate,  is  best 
adapted  to  the  district. 
1 14.  A rotation  founded  on  these  principles  has  been  for  many 
years  carried  out  on  a light  grauwacke  soil,  by  Mr.  Henry  Gatley, 
an  excellent  agriculturist  near  Truro,  and  with  the  most  satis- 
factory results.  As  it  is  well  calculated  to  raise  the  amount  of 
produce  in  the  West,  I shall  give  it  in  detail. 
