31 
i/i  its  Effect  on  Cultivation. 
To  guard  against  cold  damp  air,  farmhouses,  yards,  and  sheds 
should  be  built  on  gently-sloping  sheltered  eminences.  Gardens 
where  early  vegetables  are  desired,  should  be  situated  on  ground 
sloping  to  the  south,  with  a low  fence,  or  still  better,  a ditch  as 
the  southern  border;  a wall  for  fruit  on  the  other  sides;  the  cold 
stratum  of  air  on  the  surface  would  then  pass  down  the  slope  and 
be  replaced  by  air  4°  or  6°  warmer ; a circulation  so  produced 
would  greatly  protect  the  plants  from  injury  by  hoar-frost. 
71.  Winds. — The  temperature  and  weather  of  the  British 
Isles  are  greatly  influenced  by  the  direction  of  the  wind.  On  the 
south  and  west  lies  the  Atlantic,  sustaining  on  its  bosom  a reser- 
voir of  humid  air.  On  the  east  lies  the  cold  air  of  the  Alps,  or 
the  dry  air  of  the  great  northern  plain,  whose  surface  is  covered 
with  drift  and  gravel.  On  the  north  are  the  high  bleak  moun- 
tains of  Scandinavia,  covered  with  snow  for  half  the  year.  When 
the  wind  blows  for  a few  days  in  one  direction  it  covers  this  land 
with  the  atmosphere  of  the  region  which  it  has  traversed,  and 
impresses  its  distinctive  character  on  our  climate  ; in  fact  the  wind 
makes  the  weather.  The  general  direction  of  the  wind  is  shown 
below;  the  effects  produced  will  be  described  further  on. 
Table  X. — Showing  the  General  Direction  of  the  Wind. 
Place. 
Years. 
N. 
s. 
E. 
w. 
s.w. 
N.W. 
S.E. 
N.E. 
Number 
of 
Observa- 
tions. 
Authority. 
London 
10 
16 
18 
26 
53 
112 
50 
32 
58 
365 
Royal  Society. 
Lancaster  . 
7 
30 
51 
17 
47 
92 
26 
35 
67 
365 
Dumfries  . 
9 
36* 
38* 
68 
69 
50* 
25* 
18* 
14* 
321 
Londonderry 
7 
32 
42 
29 
109 
68 
53 
77 
32 
442 
M'Culloch. 
Truro  . . 
6 
63 
67 
90 
129 
173 
162 
114 
82 
880 
Report  Cornwall 
Bowerhope, 
kirkshire 
Set- 
10 
15 
28 
40 
71 
101 
35 
16 
22 
328 
Royal  Institution. 
C&mbuslang, 
Glasgow 
near 
7 
174 
40 
47 
104 
365 
Dr.  Meek. 
Exeter  . . 
• * 
10 
173 
188 
123 
115 
599 
Dr.  Barham. 
At  Cork  Dr.  Smith  states,  that  “it  appears  from  a regular 
diary  of  the  weather  kept  for  several  years  in  that  city,  that  the 
winds  blow  from  the  south  to  the  north-west  three-fourths  of  the 
year  at  least.” 
72.  General  effect  of  the  Climate  of  the  British  Isles  on  Vegeta- 
tion.— The  thermomelrical  distribution  of  heat  which  has  been 
described,  with  the  variable  quantity  of  moisture  which  the  soil  in 
different  localities  receives,  and  at  different  seasons,  must  produce 
a corresponding  effect  on  vegetation ; and  this  effect  is  more 
evident  in  plants  whose  distribution  is  governed  by  natural  laws, 
than  in  those  which  the  skill  or  the  wants  of  man  have  taught  him 
to  raise  in  situations  not  always  adapted  to  them. 
