I.— Astronomic Observations. 
Although this completely agrees with the mean tenour of the other 
results, the last value is for the present neglected, and, after obtaining the 
mean of each day, we get as general mean : 
11th July, 8 h 42 m . C (m = + 5 h 15 m 33 s 'l. 
From the observations taken at Bujongolo during the days following our 
arrival we had (see p. 311): 
28th June, 20 h 25 m . C (m = + 5 h 15 m 28 s 'l. 
Hence for this interval of 12*52 days we obtain the diurnal correction : 
K= + 0 s- 398 
with which we get : 
12th July, 0 h of local time . C, m = + 5 h 15 m 33 s *3 
Moment of Occupation. ,, = +5 h 15 m 33 s '2 
With this element and with the approximate longitude already obtained, 
we proceed to a first calculation of mean Greenwich time at the moment of 
emersion of B A C 81 from the lunar disk, the moment when the No. 1 
■chronometer indicated 10 h 14 m 4 s (Obs. No. 55). From the first approximation 
we got: 
Bujongolo... ... ... X = l h 59 m 59 s- 2 E.G. 
The calculation for a second approximation, in which account was also 
taken of the terms of second order, only very slightly modified the result. 
Thus: 
Bujongolo... ... ... X = l h 59 m 59 s '33 E.G. 
As, however, the value of the longitude thus obtained might be seriously 
affected by even a slight error in the lunar co-ordinates given by the 
ephemerides, we consulted some astronomic observers in order to ascertain 
whether, about the time when the expected occupation took place, any 
observations of lunar culminations had concurrently been made. This was 
done in order to introduce into the calculation the error of the position of 
the moon. 
Prof. Millosevich, Director of the Observatory of the Collegio Bomano, 
in Rome, having undertaken the determination of the longitude of Tripoli, 
where the astronomer, Dr. Bianchi, was observing transits of the moon at 
meridian, proceeded to take observations of lunar culminations at the Collegio 
Romano from the 2nd to the 7th July, 1906. From these he obtained for 
.. 11th July—time of the occupation—a correction for the right ascension of 
the moon= +0 S T8, and this agrees perceptibly with that communicated to us 
by Greenwich for the same date = + 0 S, 20. 
It may be mentioned that Greenwich also supplied us with the correction 
for that date of the lunar declination = + l s, 8. 
313 
