812     Royal  Society  .-—The  Astronomer  Royal  on  a  supposed 
instrument;  the  tabular  declination  is  affected  with  the  Received 
Aberration  used  in  the  computation  of  the  '  Nautical  Almanac ;'  and 
the  apparent  value  of  the  geographical  latitude  is  therefore  affected 
by  the  difference  between  the  True  Aberration  as  seen  in  the  instru- 
ment and  the  Received  Aberration.  If,  therefore,  under  all  circum- 
stances, and  especially  in  the  comparison  of  days  when  the  sign  of 
aberration  has  changed,  the  apparent  value  of  the  geographical  lati- 
tude is  sensibly  constant,  it  proves  that  the  True  Aberration  is  the 
same  as  the  Received  Aberration,  or  at  least  that  one  is  not  a  multiple 
of  the  other. 
The  last  column  of  the  Table  is  given  only  to  show  to  how  large 
an  extent  Aberration  enters  into  the  star's  Apparent  Declination. 
Every  result  for  Observed  Zenith-distance  in  the  Table  is  the 
mean  of  observations  in  reversed  positions  of  the  instrument. 
Day  of 
observation. 
Star's 
Observed 
Zenith- 
distance 
North. 
Star's  Decima- 
tion from 
'  Nautical 
Almanac' 
Difference  for 
Geographical 
Latitude  of 
Instrument. 
Correction 
for  Aberra- 
tion adopted 
in '  Nautical 
Almanac' 
1871. 
Feb.    28 
85-30 
85-71 
84-19 
82-18 
83-63 
84-58 
83-87 
82-73 
84-18 
84-04 
83-48 
5°1  29  59-3 
59-1 
58-9 
58-8 
58-0 
58-0 
57-9 
57-9 
58-0 
58-1 
51  29  58-2 
5°1  28  34-0 
33-4 
34-7 
36-6 
34-4 
33-4 
34-0 
35-2 
33-8 
34-1 
51  28  34-7 
-18-71 
18-82 
19-02 
19-11 
19-73 
19-74 
19-73 
19-69 
19-66 
19-59 
-19-54 
March  1  
3 
4 
16 
17 
21 
23 
24 
26 
27 
Mean  Latitude  of  Instrument  from  j  g-.   „§  04.4 
Spring  Observations J 
Aug.  29 
122-10 
121-84 
121-62 
120-27 
122-98 
122  20 
121-53 
121-38 
120-01 
120-62 
120-29 
121-31 
124-41 
120-60 
51  30  34-4 
35-0 
35-1 
35-2 
35-3 
35-4 
35-5 
35-5 
35-4 
35-1 
35-1 
350 
34-9 
51  30  34-8 
51  28  32-3 
33-2 
33-5 
34-9 
32-3 
33-2 
34-0 
34-1 
35-4 
34-5 
34-8 
33-7 
30-5 
51  28  34-2 
4-18-25 
1901 
19-18 
19-33 
19-45 
1964 
19-70 
19-74 
19-72 
19-46 
19-40 
19-33 
19-26 
+19-10 
Sept.     5 
7 
9 
11 
15 
17 
22 
24 
Oct.      1  
2 
3 
4 
6 
Mean  Latitude  0 
Autumn  Obser 
?  Instrument  fror 
vations    
a  1  51  28  33-6 
