500 
THE  ADMIEAETT  ASTEOXOmCAL  EXPEEBIEXT 
with  the  results.  August  8,  however,  opened  more  auspiciously,  and  I began  before 
sunrise;  and  with  the  assistance  of  the  mate  and  carpenter  of  the  yacht,  kept  up 
observations  continuously  throughout  the  day,  until  the  leaking  of  the  bulb  (which  had 
begun  again  in  the  middle  of  the  day,  apparently  from  some  effect  of  the  heat  twisting 
the  wood,  and  finally  splitting  the  glass)  increased  to  such  an  extent,  that  the  graduated 
tube  could  no  longer  be  kept  full. 
Considering  the  state  of  the  instrument,  the  only  purpose  that  the  obseiwations  can 
be  made  useful  for,  is  to  institute  a rude  comparison  with  the  results  of  the  black-bulb 
thermometers,  which  were  simultaneously  observed  throughout  the  day.  To  facilitate 
this  purpose,  the  actinometer  results  in  the  following  Table  have  been  multiplied  by  a 
factor,  such  as  was  found  by  trial,  to  make  the  sum  of  its  degrees  or  dirisions  throughout 
the  day,  equal  to  the  sum  of  the  thermometer  degrees.  Each  actinometer  reading  in  the 
Table  is  the  result  of  four  “ suns”  and  three  “ shades,”  corrected  for  temperatui-e  by  the 
reading  of  the  small  inserted  thermometer,  and  the  Table  given  by  Su*  J . Heeschel  in 
the  ‘ Admiralty  Manual.’  Each  black-bulb  reading  is  the  result  of  a pair  of  readings 
before  and  a pair  immediately  after  each  group  of  actinometer  observations. 
Comparison  of  Actinometer  and  Black-bulb  results  for  Solar  Badiation  on  August  8, 
on  Guajara. 
Time. 
Actinometer 
radiation. 
Black-bulb 
radiation. 
Time. 
Actinometer 
radiation. 
Black-bulb 
radiation. 
Time. 
Actinometer 
radiation. 
Black-bulb 
radiation. 
h 
m 
d 
h 
m 
d 
o \ 
h 
m 
d 
0 
5 
10 
A.M. 
- 1*8 
— 2-8 
9 
6 A.M. 
-f  88-2 
+ 100-0  i 
1 
30 
P.M. 
+ 85-1 
+ 71-0 
5 
14 
A.M. 
Sun  rose. 
9 
28  A.M. 
83-3 
100-2 
1 
54 
P.M. 
85-1 
80-8 
5 
32 
A.M. 
+ 22-5 
+ 5-4 
9 
44  A.M. 
85-0 
99-0  : 
2 
24 
P.M. 
89-9 
81-8 
5 
48 
A.M. 
36-3 
26-8 
10 
0 A.M. 
84-6 
99*3  ; 
2 
54 
P.M. 
84-2 
76-0 
6 
10 
A.M. 
56'7 
52-1 
10 
14  A.M. 
84-2 
98-2 
3 
24 
P.M. 
76-6 
72-4 
6 
24 
A.M. 
69-8 
61-2 
10 
34  A.M. 
81-1 
98-4 
3 
44 
P.M. 
83-7 
71-9  1 
6 
40 
A.M. 
63-3 
69-2 
10 
54  A.M. 
78*8 
93-7 
4 
0 
P.M. 
81-5 
71-9 
7 
4 
A.M. 
68-7 
57*6 
11 
14  A.M. 
79-3 
89-2 
4 
14 
P.M. 
71-8 
70-4 
7 
20 
A.M. 
74-4 
72-2 
11 
30  A.M. 
74-4 
87-0 
4 
32 
P.M. 
77-0 
67-9 
7 
34 
A.M. 
77-1 
79-0 
11 
44  A.M. 
72-6 
87-4 
4 
4t) 
P.M. 
75-3 
64-5 
7 
56 
A.M. 
81-1 
84-8 
0 
10  P.M.  ‘ 
94-4 
87-0 
5 
4 
P.M. 
62-0 
62-6 
8 
18 
A.M. 
82-8 
88-0 
0 
34  P.M. 
93-5 
82-9 
5 
20 
P.M. 
63-3 
58-3 
8 
32 
A.M. 
85-9 
88-0 
0 
54  P.M. 
79*7 
74-0 
5 
44 
P.M. 
+ 54-5 
+ 46-6 
8 
48 
A.M. 
+ 85-4 
+ 95-6 
1 
14  P.M. 
+ 84-2 
+ 72-0 
Actinometer 
1 broke  down. 
Much  as  might  be  expected  from  the  principle  of  the  actinometer,  it  approv  ed  itselt 
at  sunrise  as  the  more  sensitive  instrument ; but  the  cause  of  the  differences  between  the 
two  instruments  through  the  middle  of  the  day  is  not  equally  plain ; neither  of  them 
follows  the  law  of  altitude,  and  their  differences  from  each  other  are  far  beyond  eiTors 
of  observation. 
(3.)  Radiation  of  the  Moon. 
For  the  particulars  of  observations  with  the  excellent  thermo-multiplier  kindly  lent 
by  Mr.  Gassiot,  reference  may  be  made  to  volume  1,  where  the  whole  of  them  are 
entered,  with  notes  of  all  attendant  circumstances.  Here  it  may  suffice  to  state  the 
resulting  mean  quantities. 
