in  its  Effect  on  Cultivation. 
33 
74.  Our  corn-producing  plants  are  exotics — natives  of  a 
warmer  clime — their  original  locality  cannot  be  clearly  defined ; 
but  there  is  no  doubt  that  these  grains  accompanied  the  progress 
of  agriculture  from  Egypt  to  Greece,  and  were  spread  from 
thence  over  Europe.  Wheat  and  barley  have  been  found  grow- 
ing wild  in  Persia,  Mesopotamia,  and  on  the  banks  of  the  Eu- 
phrates; and  a writer  on  this  subject  in  the  “ Edinburgh  Philo- 
sophical Journal  ” for  1827  arrives  at  the  conclusion,  “ That 
the  valley  of  the  Jordan,  the  chain  of  Libanus,  or  the  parts  of 
Palestine  and  Syria  which  border  upon  Arabia,  may  with  great 
probability  be  assigned  to  our  cereals  as  their  native  country.” 
These  valuable  grains  have  been  spread  over  the  temperate 
regions  of  Europe,  where  they  are  naturalized ; and  the  hardy 
inferior  varieties  have  been  pushed  as  far  north  as  the  rigour  of 
the  climate  will  permit.  In  what  part  of  this  cereal  zone  are 
our  islands  situated  ? Certainly  not  in  that  best  adapted  for 
wheat,  which  is  grown  in  greater  perfection  on  the  plains  of  Europe, 
and  in  the  dry  hot  summers  of  Spain.  The  summer  temperature 
of  the  cultivated  lands  of  the  British  Isles  varies  from  54°  to 
64°;  in  the  fertile  plain  of  Lombardy  it  is  73° ; and  in  Sicily, 
“ the  granary  of  ancient  Rome,”  77°.  There  is  no  part  of 
Europe  where  the  wheat  crop  is  pressed  into  so  low  a summer 
temperature  as  in  these  islands,  and  that  with  a considerable 
degree  of  success.  In  1727  a small  field  of  wheat  near  Edin- 
burgh was  so  extraordinary  a phenomenon  as  to  attract  the  atten- 
tion of  the  whole  neighbourhood  ; and  up  to  1770  its  cultivation 
was  little  extended.  But  now  abundant  crops  are  seen  on  the 
lowlands,  the  most  favourable  hill  districts  are  invaded,  and  the 
culture  pushed  as  far  north  as  the  Murray  Frith,  from  whence 
some  excellent  samples  are  sent  to  the  London  market.  On  the 
north  of  Ireland,  where  Mr.  Wakefield  thought  it  would  be 
useless  to  introduce  wheat,  it  is  now  extensively  cultivated.  We 
are,  therefore,  in  a good  position  to  determine  the  effect  of 
climate  on  this  grain,  and  to  inquire  how  far  the  profitable 
cultivation  of  wheat  may  be  carried,  and  what  are  the  conditions 
of  climate  necessary  to  its  perfection. 
75.  In  order  to  obtain  a condensed  and  comprehensive  view 
of  the  effect  of  climate  on  the  wheat  crop,  I have  compiled  from 
the  meteorological  observations  of  the  Royal  Society,  from 
Tooke's  ‘ History  of  Prices,’  and  from  a Return  made  to  the 
House  of  Commons  in  1843  on  the  price  of  wheat,  the  following 
tabulated  facts,  giving  only  such  years  as  were  marked  by 
peculiar  abundance  or  deficiency.  More  minute  details  of  these 
and  other  seasons  may  be  consulted  in  the  Transactions  of  the 
Royal  Society  : — 
VOL.  xr. 
o 
