(277) 
and 7 the hour angle corresponding to the zenith distance Z, then 
we have finally: 
cos T' 
cos 4 (t — dt!) 
cost (¢+¢')= 
Whereas the observations were always made at large zenith 
distances, z — 2’ is small, therefore we sce that an approximate 
knowledge of this difference and accordingly also of the zenith-point 
will be sufficient '). 
I always made several pairs of pointings; sometimes two stars 
have been employed. 
Here follow the results obtained for the correction of my 
chronometer and the daily rates derived from them for the period 
including my observations for latitude and longitude discussed in 
the following sections, 
The corrections of the chronometer as given here are corrections 
on the mean time of Chiloango. Wor converting sideral into 
mean time the longitude of Chiloango was taken to be: 48 min. 
32 sec. east of Greenwich. In January 1901 I began noting down 
the temperature once a day, namely at 9 o’clock in the morning; 
therefrom the mean temperatures have been derived for the periods 
between the time determinations. They are given in the last column 
of the table. 
If we leave out one interval of only one day, the agreement of 
the daily rates appears to be very satisfactory. The fact that here 
temperature varies little and only very slowly, will certainly have: 
contributed to this result. Yet it is clearly visible that smaller daily 
rates correspond to lower temperatures and this is confirmed by the 
observations before October 1900; for between 15 August and 5 
September the mean daily rate was + 0.801, and between 5 Sep- 
tember and 5 October + 0.526. 
Afterwards it will be possible to apply small corrections to the 
results given here, especially for the division errors of the vertical 
circle. For the determination of the latitude the errors left as yet in the 
chronometer corrections are of no consequence and for the approxi- 
mate reduction of the observations for longitude, which is as yet 
1) As cos} (z—z') and cos} (¢—d') differ little from unity we may also in a known 
way compute the differences between Z and $(z-+-2') and between 3 (¢-+ ?¢’) and 
T directly by means of approximate formulae. 
