480 
THE  ADMIEALTY  ASTEOXOHICAL  EXPEEIIMEXT 
looking  for  them  at  greater  distances,  as  10  and  15  degrees,  there  was  ever  more  or  less 
of  a luminous  pattern  on  the  object-glass,  caused  by  the  all-powerful  sunlight  striking 
on  microscopic  imperfections  on  the  surface. 
With  all  this,  however,  1 observed  by  day  many  more  stars  than  I had  ever  done  in 
Edinburgh ; but  the  more  marked  result  was,  the  far  greater  brightness  of  the  bright 
stars.  The  preponderance  of  Sirius,  for  instance,  above  aU  other  stars,  was  never  so  power- 
fully manifested  to  me  before ; and  from  his  excessive  and  staring  rfsibHity,  one  came 
down  at  once  through  an  immense  number  of  measui’able  gradations  to  Ai'ctums,  the 
next  brightest  star  visible,  and  perhaps  arrived  at  total  in-risibility  -vrfth  a star  of  the  third 
magnitude. 
(4.)  Naked-eye  Observations. 
The  stars  shone  brilliantly,  as  seen  from  Guajara,  and  caused  the  dome  of  the  skies 
to  appear  resplendent  with  glory;  the  Milky  Way  was  a magnificent  feature  in  its 
scenery,  and  the  zodiacal  light  towards  morning  was  still  more  remarkable.  Jupiter  also 
was  surpassingly  brilliant  when  high  in  the  heavens  after  midnight ; but  1 could  never 
see  his  satellites  with  the  naked  eye,  not  even  when  eclipsing  the  planet  behind  a distant 
lava  ridge.  When  treating  the  bright  part  of  the  moon  in  a similar  manner,  the  illumi- 
nation of  the  dark  part  appeared  conspicuously,  though  the  fii'st  quarter  was  past. 
With  the  new  as  well  as  the  old  moon,  when  forming  a crescent,  the  brightness  of  the 
surface  was  such,  as,  acting  by  irradiation  on  the  eye,  to  give  an  appearance  of  unnatural 
bluntness  to  the  horns.  She  gave  one,  moreover,  at  once  and  visibly,  the  real  idea  of 
being  closer  than  the  stars ; while  the  “ shooting-stars,”  of  which  by  the  way  we  did  not 
see  any  displays  remarkable  either  for  number  or  brightness,  appeared  absm-dly  close ; 
and,  harfng  a reddish  light,  looked  even  like  sparks  of  fire  filing  through  the  aii*. 
We  were  much  struck  on  the  mountain  by  the  quiet  and  steady  planetary  light  of  the 
stars,  and  were  inclined  at  first  to  say  that  they  did  not  twinkle ; but  we  soon  found  that 
they  did  so,  though  to  a much  smaller  extent  than  in  the  plaisn  below.  Ha-ving  lately 
become  acquainted  with  Professor  Dtjfour’s  method  of  applj-ing  the  principles  of 
numerical  observation  to  the  scintillation  of  stars,  and  the  rich  results  that  he  has  akeady 
deduced  from  very  simple  beginnings,  I regret  that  I did  not  attempt  something  of  the 
same  sort  on  the  Peak ; though  perhaps  nothing  short  of  his  o-sto  skill  and  experience 
would  be  required  to  do  justice  to  the  natural  capabilities  of  the  place. 
(5.)  Qualities  of  the  Atmosphere. 
The  astronomical  qualities  of  the  atmosphere  may  be  di-vided  into  two  species, — the 
immediate  or  particular,  as  wind,  fog,  &c. ; and  the  general,  as  distant  clouds,  haze,  and  ' 
other  aerial  impurities. 
Wind  is  usually  a terrible  drawback  on  the  availability  of  mountains  for  observatory  ' 
purposes,  and  the  tops  of  the  lower  hills  in  Teneriffe,  at  about  the  level  of  the  trade-  | 
wind  cloud,  are  swept  by  it  with  terrific  force ; but  above  that  height,  the  -ufiiid,  still  i 
preserving  the  same  N.E.  direction,  continually  decreases  m strength,  until  it  reaches  a I 
