506 
THE  ADMIEALTT  ASTEOXOMICAL  EXPEETAfRXT 
the  neighbourhood,  does  not  differ  much  from  the  solar  spectrum ; but  Xos.  14,  15,  and 
16  show  that  such  a spectrum,  with  the  sun  somewhat  low,  as  20°,  has  neither  lines  nor 
light  at  the  red  end,  but  that  they  gradually  increase  as  we  try  the  lower  regions  of  the 
sky,  showing  there  the  remarkable  multitude  of  lines  beyond  D. 
Taking  together  the  whole  of  the  sky  spectrums,  12  to  17,  and  comparing  them  with 
those  of  the  sun,  we  find  that  C is  not  marked  in  circumstances  where  it  might  be 
expected ; and  when  it  does  appear,  it  is  overpowered  by  the  “ gro'^fing  ” line  in  the' 
direction  of  D.  Likewise  D is  overpowered  by  the  numerous  broad  bands  beyond  it ; so 
that  when  the  spectrum  is  seen  faintly,  those  variable  lines  might  easily  be  mistaken  for 
C and  D,  and  a greater  degree  of  identity  might  thence  be  considered  to  prevail  between 
the  sun  and  sky  spectrums  than  actually  obtains. 
Red  Ends  of  Lunar  Spectrums. 
The  moon  was  not  well  situated  for  spectrum  observations,  though  drawings  were 
obtained  on  August  13th  and  15th,  at  altitudes  of  25°  and  38°;  and  at  times,  two  days 
before,  and  on  the  night  of,  the  full  moon. 
The  most  striking  feature  was  the  blood-red  character  of  the  red  end;  beyond  the 
extreme  intensity  of  this  colour,  the  other  tints  had  nothing  notably  different  from  a sun 
spectrum.  Notwithstanding  the  amount  of  red  light,  no  lines  could  be  perceived  there : 
in  this  circumstance  was  a striking  difference  to  the  low  sun  spectrums,  where,  as  the 
red  became  predominant,  the  number,  size  and  visibility  of  the  lines  in  the  red  increased 
also.  The  first  line  identified  in  advancing  from  the  red  end,  was  the  growing  fine 
between  C and  D ; from  thence  was  a long  blank  space  until  three  fine  lines  near  E were 
seen,  then  E and  F.  These  observations  were  direct. 
Violet  End  of  the  Spectrum. 
Eight  drawings  of  the  violet  end  of  the  sun’s  spectrum,  two  of  the  sky’s,  and  two  of 
the  moon’s  were  obtained ; but  I do  not  think  them  worth  engraving  here,  as  most  of 
them  labour  under  the  untoAvard  effects  of  the  speculum.  It  may  suffice  to  remark, 
that  at  Guajara,  the  vertical  sun  spectrum  terminated  beyond  H,  while  the  horizontal 
sun  spectrum  was  so  shortened  at  that  end  as  to  terminate  between  H and  G. 
Again,  comparing  a high  sun  spectrum  at  the  sea-level  Avith  a similar  one  at  Alta 
Vista,  10,702  feet  high,  both  obseiwed  dfrect,  it  was  foimd  that  AAliile  in  the  former  the 
spectrum  terminated  immediately  beyond  H,  and  the  tAvo  bars  of  H AA^ere  nebulous,  in 
the  latter  the  spectrum  extended  beyond  H to  three  times  the  distance  of  its  bars 
asunder : the  two  said  bars  also  lost  all  their  nebulosity,  being  clearly  resolved  into  tlieir 
component  lines ; many  fine  clear  lines  were  seen  betAveen  them,  and  many  appeared 
nebulously  in  the  space  beyond.  In  the  sky  spectrums,  and  more  particularly  in  tliose 
of  the  moon,  the  prominence  of  G was  remarkable ; next  came  F,  Avhile  H was  nearly  it 
not  quite  invisible. 
