ON SOLAR PHYSICS. 
391 
results, while from the Ivew series we derive 60. On the whole, we have adopted 60 as 
the most probable multiplier, and by this number the measurements deduced from 
Schwabe, according to the arbitrary scale, have been multiplied in order to bring them 
to agree with the Ivew scale, of which the unit is one-milliontli of the sun’s visible 
hemisphere. 
25. Applying this multiplier to each of the fortnightly results from Schwabe exhi- 
bited in Table IV., and considering Carrington and Kew as absolutely accurate, we obtain 
the following Table, which gives a general idea of the trustworthiness of a fortnight’s 
observation of Schwabe. 
Table V. 
No. of series. 
Date. 
Schwabe X 60. 
Standard. 
]. 
1854. 
Dec. 1—15 
162 
105 
Nov. 16-30 
570 
565 
3. 
Sept. 1-15 
204 
215 
4. 
Sept. 16-30 
138 
138 
5. 
1859- 
Dec. 1-15 
1092 
1 222 
6. 
Dec. 16-31 
984 
1060 
/ • 
1862. . 
April 20 to May 1 
714 
698 
8. 
1863. 
Jan. 1-15 
1296 
1511 
9. 
Jan. 16-31 
942 
901 
10. 
May 1-15 
810 
622 
11. 
May 16-31 
798 
812 
This is we think a very satisfactory result, showing that the mean spotted area derived 
from a single fortnight of Schwabe is never probably far from the truth. 
If instead of a single fortnight we take the mean of six fortnights, we derive the fol- 
lowing Table : — 
Table VI. 
Series. 
Schwabe, 
mean of 6 fortnights. 
Standard, 
mean of 6 fortnights. 
1-6 
525 
551 
2-7 
617 
649 
3-8 
738 
807 
4-9 
861 
921 
9-10 
973 
1002 
10-11 
924 
934 
which exhibits the very great trustworthiness of the means of six fortnights, or three 
months of Schwabe’s observations. 
26. TV e ought to add that, in estimating the spotted area of the various groups from 
Schwabe’s pictures, we applied an approximate multiplier on account of foreshortening 
when the group was near the limb ; but this was a part of the process on which we 
3 h 2 
