in  its  Effect  on  Cultivation. 
23 
56.  A review  of  the  facts  which  have  been  thus  shortly  stated 
leads  irresistibly  to  the  conclusion,  that  much  of  the  peculiarity 
of  our  climate  is  produced,  not  by  the  ordinary  effects  of  oceanic 
influence,  but  by  the  vast  movements  of  the  sea,  which  have  been 
described.  It  is  therefore  no  flight  of  fancy  to  assert,  that  we  are 
indebted  to  the  continuous  mountain  chain  of  the  Andes  for  our 
agricultural  position  and  prosperity.  Let  the  Isthmus  of  Panama, 
which  now  intercepts  and  diverts  the  Equatorial  current,  be  wholly 
swept  away,  and  it  would  produce  a greater  revolution  in  Britain 
than  arms  or  science  ever  effected. 
57.  It  is  found  that  the  air  over  the  sea  has  a mean  temperature 
of  about  2°  below  that  of  the  surface-water.  Captain  Sabine 
remarks,  that  “ the  temperature  of  the  air  is  known  to  he  immedi- 
ately dependent  on  that  of  the  surface-water  of  the  sea,  and  to  be 
influenced  nearly  to  the  full  extent  of  any  alteration  that  may  take 
place  therein”  In  the  Gulf  of  Guinea  the  temperature  of  the 
water  and  the  air  was  changed  by  the  currents  in  a few  days’  sail 
as  follows : — 
Mean  of  Sea.  Mean  of  Air. 
The  Guinea  current  . . . 83°  . . . 81°  *5 
The  Equatorial  current  . . 73  . . . 74  * 
58.  In  order  to  determine  the  effect  of  the  sea  on  the  climate 
of  the  western  coast  in  winter,  I have  had  a register  kept  of  the 
temperature  of  the  surface-water  of  the  sea  at  St.  Agnes,  an  open, 
exposed  part  of  the  north  coast  of  Cornwall,  and  the  following  are 
the  results  deduced  from  146  observations  :f — 
Oct. 
Nov. 
Dec. 
Year. 
o 
0 
o 
Mean  temperature  of  the  Burface  water  of  the  sea 
54-8 
53-5 
50-3 
1849 
Mean  temperature  of  the  air  at  Roy.  Inst.,  Truro 
52-9 
49  • 6 
42-9 
1849 
Excess  of  temperature  of  the  sea  above  the  air 
1 -9 
3-9 
7-1 
From  these  observations  it  appears  that  the  warmer  waters  of 
the  sea  must,  in  the  depth  of  winter,  considerably  influence  the 
temperature  of  the  adjoining  air.  In  the  month  of  December  the 
sea  is  ordinarily  6°  above  the  air,  but,  in  consequence  of  the  frost 
in  that  month  last  year,  the  excess  amounted  to  7° ’4.  During 
the  continuance  of  the  frost,  the  thermometer  in  the  air  sunk  to 
20°,  when  the  lowest  temperature  of  the  sea  was  46°.  It  is  there- 
fore not  surprising  that  snow  never  lies  along  the  coast,  and  that 
frost  is  of  short  continuance. 
The  difference  in  the  temperature  of  the  sea-water  at  day  and 
* Phil.  Mag.,  June,  1826,  p.  428. 
f For  detailed  observations,  tee  Appendix  No.  2. 
