621 
in  its  Effect  on  Cultivation. 
rushes  towards  the  equator  to  supply  the  place  of  the  air  which 
by  the  action  of  the  sun’s  rays  is  there  continually  ascending  into 
the  higher  regions  of  the  atmosphere. 
The  rotatory  motion  of  the  earth  being  much  greater  at  the 
equator  than  near  the  poles,  the  wind  cannot  at  once  accommo- 
date itself  to  the  increased  motion  of  the  earth’s  surface  towards 
the  east,  and  consequently  lags  behind , and  appears  to  move  in 
a south-westerly  direction,  or  from  the  north-east.  The  sea  and 
land  breezes  also  depend  on  the  same  principle:  the  land  being 
more  heated  by  the  sun  during  the  day  causes  a wind  from  the 
sea  towards  the  land,  but  during  the  night  the  land  being 
cooled  by  radiation  there  is  a breeze  from  the  land  to  the  sea. 
The  peculiar  position  of  the  continents  of  Europe  and  Asia 
causes  a land  and  sea  breeze  on  a gigantic  scale , having  for 
its  period  Tiot  24  hours,  but  the  whole  year  ; winter  and  spring 
answering  to  the  night  or  land-breeze , and  summer  and  autumn 
answering  to  the  day  or  the  prevalence  of  the  sea-breeze.  Tlius, 
according  to  the  intensity  of  the  sun’s  rays  on  the  vast  continent 
of  Europe  and  Asia  during  the  summer  will  be  the  regularity 
of  the  westerly  and  south-westerly  winds  during  summer  and 
autumn;  and  in  proportion  to  the  cold  of  winter  on  the  same 
continent  will  be  the  regularity  of  our  easterly  and  north-easterly 
winds  during  winter  and  spring.  Except,  owing  to  local  pecu- 
liarities, the  former  of  these  winds  (the  western)  is  so  regular 
that  from  June  to  November  there  is  rarely  for  two  days  together 
a wind  blowing  in  any  other  direction  ; and  that  the  latter,  the 
eastern  winds,  are  fortunately  not  equally  regular  is  owing  to  the 
current  of  air  from  the  continent  setting  strongly  towards  the 
equator  across  the  Indian  Ocean  causing  the  monsoons,  and  this 
air.  on  arriving  at  the  equator,  being  heated  and  rising  till  its 
elasticity  overcomes  the  density  of  the  air  near  it,  it  flows  back 
in  an  upper  current  towards  the  poles.  But  coming  from  the 
equator,  its  motion  of  rotation  is  greater  than  that  of  the  air 
farther  from  the  equator,  and  thus  it  will  apparently  have  a 
motion  from  west  to  east,  and  when,  by  being  condensed  by  the 
cold  of  the  upper  regions,  it  falls  down  to  the  surface  of  the  earth, 
its  motion  will  counteract  the  regular  motion  from  east  to  west, 
and  cause  variable  winds,  which  are  hence  far  more  common 
during  winter  and  spring  than  during  summer  or  autumn.  In 
Scotland,  especially  on  the  Highlands,  the  winds  are  extremely 
variable,  yet  the  general  tendency  along  the  western  isles,  also 
along  the  western  coast,  when  they  have  not  been  interrupted  by 
the  mountains  of  Skye,  and  in  the  Shetland  and  Orkney  Islands, 
is  for  fully  two-thirds  of  the  year  from  the  west.  But  among 
the  Highland  mountains,  when  any  of  the  valleys  are  heated  by 
the  rays  of  the  sun,  the  wind  rushes  with  violence  through  the 
VOL.  xi.  2 s 
