Introduction 
Vll 
Longitude of the ascending node of sun’s equator = 73° 40' for 1850. 
Inclination of axis to axis of ecliptic = 7 0 15'. 
(These were the values recommended by Carrington.) 
Mean daily rotation angle =842.'o4 = i4?o34, 
or Mean sidereal rotation period =25.652 days. 
This value was derived by Dr. Peters from his observations of 803 positions of 286 spots made at Naples in the 
thirteen months from September 1845 to October 1846, as stated in his paper read at the Providence meeting of the 
American Association, 1855. 
“First solar meridian that in which the earth was at Greenwich mean noon i860 January o.” 
“I reckon the longitudes in the sense that any point of the heavens would, as a result of the sun’s rotation, suc¬ 
cessively pass increasing meridians. This would correspond on the earth to counting longitudes westward as posi¬ 
tive” ( A . N., 71, 241, 1868). 
“To avoid ambiguity, it may be prefaced that the heliographical longitudes are counted in the direction opposite 
to that of the rotation of the sun (or what corresponds upon the earth from the east toward the west), and a spot is 
said to be following another neighboring one, when the former has greater heliographical longitude,—when by the rota¬ 
tion of the sun, it will come later into the same heliocentric position in regard to the fixed stars than the preceding 
spot.” {Astronomical Notices , No. 29, March 18, 1862.) 
In order to facilitate the comparison of longitudes given by Peters with those of Carrington and those at Kew 
and at Greenwich, a conversion-table is given for each date of observation by Peters. A rigorous comparison can¬ 
not be made with Carrington’s positions, as the latter were derived from assumed values of the longitude of the node 
and inclination, to which small corrections were obtained by Carrington from his whole series of observations. The 
difference is not, however, of any consequence in the identification of spots. 
The following table, which has been calculated by Mr. Philip Fox, gives the angular distances between the 
prime meridians of the systems of Carrington and Peters for Clinton noon of each day when Peters observed. The 
conversion is effected by merely subtracting Peters’ L' from the tabular value for the date (increased by 360° where 
necessary), after due allowance has been made for the difference in time of observation and in longitude of the place 
of observation. 
Table of Angular Distances Between the Prime Meridians of Peters and Carrington 
For Clinton noon of each day on which Peters observed. 
i860 
July 11 
206?02 
Sept. 25 
I 94 -59 
Dec. 15 
182^40 
May 
23 
213-39 
i 5 
205.4I 
26 
•44 
2 3 
181.20 
24 
.24 
18 
204.96 
28 
•13 
2 5 
.08 
20 
.66 
30 
193 83 
1861 
29 
212.48 
22 
• 3 6 
Oct. 6 
192.93 
Jan. 2 
i 7 9 ? 7 ° 
June 
3 
211.73 
24 
.06 
7 
•78 
4 
•39 
4 
•58 
28 
203.46 
10 
•33 
5 
•25 
5 
•43 
30 
. 16 
12 
•°3 
12 
178.19 
6 
.28 
3 1 
.01 
15 
191.58 
22 
176.69 
11 
210.53 
Aug. 1 
202.86 
16 
•43 
23 
•54 
12 
•38 
3 
• 5 6 
18 
•13 
25 
• 24 
13 
•23 
5 
. 26 
!9 
190.98 
27 
1 75•94 
14 
.08 
6 
. 11 
24 
. 22 
Feb. 1 
.18 
15 
209.93 
11 
201.35 
25 
.07 
6 
174-43 
16 
•78 
i 5 
200.75 
27 
189.77 
12 
I 73•53 
J 7 
•63 
16 
.60 
30 
•32 
14 
•23 
18 
.48 
17 
•45 
3 1 
• J 7 
16 
I 72-93 
J 9 
•33 
18 
•30 
Nov. 4 
188.57 
22 
.02 
20 
•17 
*9 
•i 5 
5 
• 42 
25 
T-l'-Sl 
27 
208.12 
20 
.00 
7 
. 12 
26 
.42 
28 
207.97 
Sept. 15 
196.09 
8 
187.97 
27 
.27 
3 ° 
.67 
17 
I 95-79 
16 
186.76 
28 
.12 
July 
4 
.07 
18 
• 64 
22 
185.86 
Mar. 4 
170.52 
6 
206.77 
20 
•34 
24 
•56 
7 
.07 
7 
.62 
22 
•04 
25 
• 41 
11 
169.47 
8 
•47 
23 
194.89 
28 
184.96 
15 
168.87 
9 
•32 
24 
•74 
Dec. 14 
i 82-55 
16 
T 2 
