¢ doe) 
The first column contains the ordinal numbers of each period of 
10 days, the second and fourth columns contain the half sums of 
Up and Uy in the two suppositions: that the correction of the 
constant of collimation mentioned in §§8 and 9 has, or has not been 
applied. The degree of precision of these numbers can be derived 
from the values of half the differences }(Ug— Uy) which, if the 
observations are correct, must be equal to 0. 
I have formed the means from each set of three successive values 
of '/, (Us + Up) and have represented them graphically in Fig. 2. 
Fig. 2. 
XO, (GR RY Sneak et er Rn ERIS 
Lj fi i ' 1 ' ni! | t j ae ‘ af ‘ 
ik SAI AS GRY is * = ren Ii a 
| 
If we try to represent the numbers !', (Ug + Uy) of the 4th column 
by an ordinary sinusoid and, assuming that this formula is exact 
for the middle-epoch, we reckon the time t in days from May 19th 
1888, we obtain the following formula for the influence of the motion 
of the pole on the azimuth of the meridian marks at Leiden: 
t + 19°.0) 
360 
U = 08.0148 Sin (= 
430,66 
Column 6 of table III gives the differences of the results accor- 
ding to this formula and the observed quantities in column 4. Accor- 
ding to this formula the influence of the motion of the pole on the 
azimuth is 0 on April 26th 1888; at that moment the latitude of 
Leiden resulting from that periodic variation attained its maximum. 
The amplitude a of the circular motion of the pole, is found from 
the amplitude of the variation of azimuth 0.0148 by means of the formula 
a= 15 X 0.0148 Cos p = 0."136 
in which p represents the latitude of Leiden, 
