48 Proceedings of Royal Society of Edinburgh. [sess. 
six nights on which observations were not secured at one or more of 
the observatories. Professor A. Auwers of Berlin rendered an 
inestimable service to science by coming to the Cape and sharing 
with me the work of observing the planet in 1889. 
It is impossible, within limits of a communication like the present, 
to do further than state the general results arrived at. 
A discussion of the combined meridian and heliometer observa- 
tions in the triangulation gives positions of the comparison stars, of 
which the probable error in either co-ordinate hardly exceeded 
±0"'03 (see Astron. Nach.^ Nos. 3107-8). 
The observations were discussed in groups, with the following 
results for the mean solar horizontal parallax : — 
Group 
I. 
June 
Limits of 
Group. 
10-12 
Mean Solar 
Parallax. 
... 8"-723 ... 
Relative 
Weight. 
0-8 
3 ) 
II. 
55 
15-19 
•804 ... 
12-3 
3 ) 
III. 
3 ’ 
19-26 
•828 ... 
15-4 
35 
IV. 
„ 26-July 3 
•872 ... 
29-2 
53 
V. 
July 
3-9 
•789 ... 
9-8 
55 
VI. 
55 
9-12 
•857 ... 
17-5 
55 
VII. 
33 
15-20 
•793 ... 
19-5 
55 
VIII. 
33 
20-23 
•809 ... 
20-0 
53 
IX. 
53 
23-25 
•742 ... 
14-0 
55 
X. 
35 
25-28 
•806 ... 
11-2 
55 
XI. 
„ 28 
-Aug. 4 
•777 ... 
33-4 
35 
XII. 
Aug. 
4-10 
•826 ... 
20-0 
33 
XIII. 
35 
10-17 
•816 ... 
26-0 
53 
XIV. 
53 
17-22 
•819 ... 
19-9 
35 
XV. 
33 
22-27 
•738 ... 
13-3 
Whence in the mean 
7t = 8"-809, prob. error ±0"’0066. 
From the diurnal parallax derived from Cape observations only, 
there resulted — 
7t = 8"‘822, prob. error ±0''-014. 
It was further found that the observed and tabular places of the 
planet could not be represented within possible error of observation 
without a periodic term nearly identical with that of the moon’s 
