496 
THE  ADMIKALTY  ASTEOYO:\nCAL  EXPEEDIEYT 
at  a distance  of  half  an  inch  apart,  and  had  their  faces  covered  with  tinfoil.  The 
box  was  further  bored  with  holes  above  and  below,  to  allow  the  circulation  of  air ; but 
in  spite  of  all  these  precautions,  the  shaded  thermometer  was  influenced  to  about  one- 
tenth  to  one-flfteenth  of  the  existing  radiation ; I have  therefore  found  it  necessary  in 
the  reductions  to  reduce  the  shaded  black  bulb  to  the  true  shade  temperature,  by  refer- 
ence to  the  observations  made  more  or  less  frequently  ^vith  the  dry  bulb  thermometer 
in  the  meteorological  veranda. 
Extensive  series  of  observations  were  only  made  at  Guajara,  as  accidents  subsequently 
occurred  to  the  instruments  at  Alta  Vista  and  Orotava.  Some  important  observations 
were,  however,  obtained  at  the  latter  stations,  which  may  serve  comparative  purposes. 
Maximum  Radiation. 
Observations  to  this  end  were  made  at  Guajara  on  July  31,  August  1,  3,  4,  5,  7,  8,  9 
and  10.  Rejecting  July  31  and  August  7,  on  account  of  the  riolent  wind,  dust-haze 
and  clouds,  we  have  the  following  quantities  for  the  radiation,  or  the  excess  of  the 
exposed  black  bulb  above  the  thermometer  in  the  shade : — 
August  1,  at  11  48  a.m.,  radiation  = 102 ’5, 
August  3,  at  0 31  p.m.,  radiation  = HIT, 
August  4,  at  9 33  a.m.,  radiation  = 121 ’3, 
August  5,  at  10  40  a.m.,  radiation  = 120'4+a.’, 
August  8,  at  9 14  a.m.,  radiation  =113‘3, 
August  9,  at  9 26  a.m.,  radiation  =120'0 +.3;, 
August  10,  at  11  0 a.m.,  radiation  =116'0+.r, 
temperatiu’e  = 6 7 T 
temperature  = 65  ’0 
temperatru’e  = 5 6 • 0 
temperatru'e  = 5 7 • 6 
temperatui'e  = 60’4 
temperatru’e  = 58-0 
temperature  =62’0 
Mean  of 
7 obs. 
jAugust  6,  at  10  36  a.m.. 
radiation  = 11 4’9-|-^  X f , temperature  = 60-9 
At  Orotava,  observations  on  August  27  gave — 
b m o o 
At  11  33  a.m.,  radiation  = 99’8+a.’,  temperature  =78-2, 
and  at  Alta  Vista,  observations  on  September  1 and  2 gave, — 
b m ^ ^ „ 
Sept.  1,  at  8 46  a.m.,  radiation  =12 7 ’8+ a’,  temperature  =49-2 
Sept.  2,  at  9 30  a.m.,  radiation  =127’5+.r,  temperature  =49-5 
Meanoflge  1-5,  at  9 
2 obs.  J 
8 a.m.,  radiation  =12 7’6-j-a%  temperature  = 49 ’3 
The  expression  fl-a?  used  above  indicates  that  the  mercury  had  risen  through  the 
whole  length  of  the  radiation  thermometer-tube  178°  or  179°,  and  was  accumulatmg 
to  an  unknown  extent  in  the  small  bulb  which  the  maker  had  fortunately  constructed 
there.  , A third  radiation  thermometer,  kindly  procured  for  us  by  Dr.  Lee,  at  his 
expense,  without  such  an  upper  bulb,  was  broken  from  this  cause,  I am  sorry  to  say,  on 
the  first  day  of  observation  at  Guajara,  before  we  had  become  aware  of  the  intense  force 
of  the  direct  rays  of  a mountain  sun. 
