528 
THE  ADMIEALTT  ASTEOKOMICAL  EXPEEBIEXT 
tion  of  the  lower  polar  current.  At  the  sea-level  there  was  a similar  absence  of  electri- 
city during  the  summer ; but  I have  since  been  informed  by  a letter  from  my  friend 
Mr,  Hamilton  of  Santa  Cruz,  that  when  the  autumn  set  in  there  below  in  Xovember, 
as  it  had  done  above  in  September,  it  brought  S.W,  wind,  rain,  and  snow  with  it,  and 
so  much  electricity,  that  a house  in  Orotava  was  destroyed  by  hghtning. 
(9.)  Alta  Vista  Storm  of  September  lAth. 
From  August  30th  a decided  change  from  the  long-continued  routine  of  the  summer 
weather  took  place ; a cirrous  cloud  formed  on  the  Peak  that  day,  immediately  above 
our  heads  at  Alta  Vista;  and  the  appearance  of  the  fibres  of  misty  cirri  dissolving, 
reforming,  and  driving  over  the  mountain  top,  was  dazzlingly  beautiful.  I have  had 
abundant  experience  of  ordinary  clouds  on  mountain  tops,  under  6000  feet  in  height ; 
but  they  were  always  dull  foggy  mist,  in  fact  Newton’s  “ grosser  clouds ; ” and  I can 
therefore  speak  positively  to  this  “ chrous  ” cloud  on  the  Peak  being  something  unusual 
in  its  nature  and  mode  of  composition.  A strong  S.W.  wind  blew  subsequently  for 
three  days ; and  though  the  weather  settled  again,  we  could  not  but  be  struck  with  the 
change  that  had  occurred  in  the  N.E.  cloud.  Still  it  formed  its  usual  stratum  at  about 
4000  to  6000  feet  high,  but  its  long  rolls  of  cumuloni  were  broken  up  into  separate  and 
distinct  cumuli ; and  on  the  south  side  of  both  Tenerifie  and  Grand  Canary  we  could  see 
similar  bodies  of  clouds  advancing  from  the  S.W.,  climbing  the  steep  sides  of  the  island, 
and  contesting  the  possession  of  the  ridges  day  after  day  Muth  the  N.E.  clouds.  This 
remarkable  aerial  combat  was  carried  on  under  our  eyes  with  various  success  until  Sep- 
tember 11th,  when  the  S.W.  cloud  obtained  a preponderance,  with  a smking  barometer. 
The  next  day  the  S.W.  cloud  was  decidedly  the  victor,  while  the  N.E.  cloud,  simply  to 
describe  the  actual  facts,  was  retiring  before  it  in  broken  and  disorganized  masses.  The 
following  day  the  barometer  rose  from  20‘363  to  20'410,  and  the  succeeding  morning, 
the  14th,  to  20‘473;  at  this  time,  however,  were  perceived  on  the  sea,  between  Tenerifie 
and  Grand  Canary,  extraordinary  appearances  of  some  miusual  and  grand  cmnent  from 
the  S.W.,  for  there  were  long  curved  lines  traceable  for  fifty  or  more  miles  in  their 
length,  indicating  a stream  setting  in  between  Tenerifie  and  Canary.  The  sky  soon  after 
became  cloudy  above  our  heads ; at  1 p.m.  a sudden  and  heary  shower  of  rain  and  hail 
came  down ; at  5 p.m.  the  cloud  descended  upon  Alta  Vista ; and  at  7 p.m.  hea^y  rain 
began  with  a violent  wind  from  the  S.,  producing  more  than  2 inches  of  rain  in  a gauge 
before  the  next  morning. 
During  this  period  the  barometer  remained  almost  stationary,  the  temperature  was 
lowered  five  or  six  degrees ; but  the  remarkable  change  was  in  the  dew-pomt.  At  9 a.m., 
on  the  14th,  the  amount  of  depression  was  46°T ; at  3 p.m.  it  was  22°‘5 ; at  5 p.ii.  2°'5; 
and  at  10  p.m.  as  low  as  0°'8. 
On  the  15th  the  depression  was  as  low  as  0°'5,  but  the  active  part  of  the  storm  had 
passed ; the  wind,  which  had  been  estimated  during  the  preHous  night  at  a velocity  of 
fifteen  miles  per  hour,  lowered  to  seven  and  to  five,  the  cloud  elevated  itself  so  as  just 
