I.—Astronomic Observations. 
Referring the daily values of the absolute correction to the mean date of 
the values of the last double series we get: 
31st July (civil) (p.m.), t c = 10' 1 26 m 48 s ...K^ — + 3" 33 m 5 s * 0 
which represents the absolute correction of the chronometer on Greenwich time 
before starting on the return journey from Fort Portal to Entebbe. On 
reaching the latter place it was found impossible to get a new telegraphic 
comparison with Mombasa, as on the outward journey. Hence proceeded to 
the determination of the absolute correction of the chronometer, using for 
Entebbe the longitude 2 h 9 m 47 s East Greenwich given us by the competent 
local authority. The result was: 
16th August.- 
-Obs. No. 110 ; f e =10 h 29 ra 
7 s ., 
.. K 1 =+3 h 33 m 
29 s - 9 
16th „ 
5 5 
111 ; „ = 10 31 
13 
55 = 
28-5 
17 th „ 
55 
112; „= 2 43 
55 
55 = 
25 • 2 
17th „ 
55 
113; „=- 2 46 
1 
,, = 
23 • 8 
We see a priori that in this interval of little over 16 hours the movement 
of the chronometer indicates a strong variation, such as had never occurred 
during the whole journey. Instead of taking the mean of these values, it was 
thought expedient to use the results alone of the two series of 16th August 
observed immediately after the arrival at Entebbe. From these we get: 
16th August (civil), (p.m.): 10 h 30 m 10 s ...Iv 1 = + 3 h 33 m 29 s- 2 
so that the daily correction of the chronometer to be used in the interval from 
31st July to 15 th August was : 
Kj = + l s -510. 
The question now was to see what degree of confidence might be placed 
in the daily corrections which had so far been obtained. From the fact that 
the longitude of a few points was determined both on the outward and the 
return journey, we were offered a means of control which, if it stood alone, 
would not be absolutely safe, since it was always possible that the errors by 
which the accepted daily corrections might be affected might be such, in 
magnitude and sign (plus or minus), as to lead to longitudinal results apparently 
concordant though really very incorrect. As, however, there were several 
points determined under such conditions, so that in some cases we could 
ascertain the degree of concordance in the longitudinal results, from this might 
be inferred both the practical value of the daily corrections that had been 
adopted, and the measure of confidence that might be placed in the positions 
obtained from the astronomic observations. 
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