( 484 ) 
The following may be remarked about the accuracy attained : 
For the mean error of one result from two zenith distances += 0"4551) 
was found as mean value; the mean error of each final result, 
derived from say 128 double observations, was then caleulated in 
different manners to be + O"065. 
For the determinations of azimuth the mean error 
of a single determination was found to be + 122, 
hence that of the mean of 12 determinations + 0,355. 
The amount of all these mean errors can very well stand a com- 
parison with the determinations of other observers. 
To this criticism of the determinations executed for geodetic pur- 
poses two appendices are added, namely : 
I. “A comparison between the latitude, determined at the station 
Utrecht, Cathedral tower (Domtoren), by Mr. Posrnumus Mryses, and 
the determinations made at the Observatory.” 
The final result of this investigation was the following: Latitude 
of the Universal instrument at the Observatory : 
derived from observations of cireummeridian 
zenith distances. ss. te ke) Se) ek RODE 
derived from the observations in the prime vertical 52 5 10,29, 
= » >» result of Mr. Postoumus Mrysns, reduced 
from the “Domtoren” to the Observatory . . . 52 5 9,84. 
This agreement is quite satisfactory, especially if we consider that 
the observations of the cireummeridian zenith distances at the Obser- 
vatory, which had been made for exercise, were executed in only one 
position of the vertical circle, which was also a motive for neglecting 
the polar motion. 
II. “A comparison between the azimuth of Amersfoort, determined 
by the author in 1879 and ’80, and the same azimuth determined 
by Mr. Postnumus Mrysrs in 1896.” 
The final result of this comparison, after due regard was paid to 
all reductions, was: Azimuth Utrecht (Centre) — Amersfoort (Centre): 
Determination of 1879,80: 68° 22’ 44"71 + 0'31, 
5 a) SoG 15159 = 0:29. 
Between these two determinations there is a difference of 0’’88 
+ 0’’42 (mean error), which partly may be explained by the acci- 
dental errors of the observation and the graduation, and partly by 
the uncertainty in the different reductions which occur in this com- 
parison. We should also bear in mind that in the results of Mr. Posruumus 
1) For Mr. Pannekoek + 0'49, for Mr. P. Meyses + O42, two numbers that 
are nearly reciprocal to the magnifying powers of the telescopes of the two 
instruments (60 and 68 times). 
