396 Scientific Proceedings, Royal Dublin Society. 
I now come to the actual observations, which were made at 
Dunsink, on every available opportunity, between February 9th 
(when my attention was first directed to the spot) and March 16th. 
The first four observations were made by my assistant, Mr. Charles — | 
Martin ; the others by myself. 
In the following table (p. 397) I give the actually observed times 
of transit expressed in Greenwich mean time, the three corrections 
referred to above, and the corrected times of central transit. In 
the last column is given the number of revolutions which had 
taken place since the first observation. 
We have next to consider the treatment of the observations 
for the deduction of the period of rotation. We must assume 
that each of these observations, the first included, is affected with 
a certain amount of error. If then we assume that the first 
transit took place at some epoch (Z,) nearly, but not exactly, 
coincident with the time of the first observation (71), and if we 
denote the number of revolutions which have elapsed between 
JT, and any subsequent transit by 7, each observation will give 
us an equation of the form— 
OA Weep ached Lh 
Now, if we take 7, = 7, +, where wv is a small correction to 
be determined, and P = P, + y where P, = 9° 55™ 348, and y is a 
small correction, we have 
T,+e+7(Po+y)=T, 
or erry= T,— 7, —7rPo =n. 
In this way we find the following equations of condition, 
taking 7, = Feb. 9th, 8° 12™ 565 (G. M. 'T.) :— 
No. Equations of Condition. Residuals. Weight. Observer. 
1. c+ O.y= 0 — 1™ 248 1 C.M. 
2. e+ 3 y=- 311 +3 40 1 6 
3. t+ d.y=+ 186 —-4 33 = 5 
4, e+10.y=— 92 fo eal 1 ie 
5. 2+27.y=—-1038 + 1 1 A.A.R 
6. 2+ 29. ¥=-— 186 + 38 1 55 
the E484. y= 28 = 118 1 f 
8. e+41l.y=- 36 -1 15 1 of 
Sh 2+651.y=—107 - 10 1 Py 
LO: 2+70.y=-118 el 1 as 
De “2+ 87. y =— 204 +1 4 1 5 
Zee 
