Dd4 
Mecca hs de 
221 245 283 20"9 24"2 22°5 25' 23" 
The results from the two series for Jidda are: 
21° 29' 147.5 + 17.7 
29 18.5 +1 .3 
The difference between them a little exceeds the sum of their mean 
errors. Forming for the first series separate results for the two 
observers we obtain : 
SCHELTEMA 21° 29'15"1 
SALIM 13.9 
which are in good accordance. 
After full consideration the two series have been united according 
to their weights and so our final results are: 
pJimva 21° 29170 1.0 
pMrcca 21° 25’ 23"1 + 1'.5 
5. Results of the determinations of time. 
The determinations of time were always made by observing the 
altitude of a star in the east and of one in the west. Each star was 
observed in the two positions of the instrument and each time the 
transits over both the horizontal threads were noted, the instrument 
remaining clamped. Hence the zenithpoint for the mean of the two 
threads was employed in deducing the zenith-distance, and for the 
mean of the two instants the hour angle was then computed after the 
usual formula 
cos Z — sin g sin d 
COST == 
cos g cos d i 
In Nov.—Dec. 1910 the chronometer of Cummins and since the 
2ad half of January 1911 that of Dent was used for the observations. 
The rates of Cummins were very great and irregular until it 
stopped altogether. I therefore omit the communication of the 
chronometer-corrections and rates for the first period. They were 
only used for the reduction of the latitude determinations and they 
were sufficiently accurate for that purpose. 
About the determinations of time in the second period I shall first 
give the necessary data to form a judgment of the accuracy reached 
as regards systematic and accidental errors. The two following tables 
contain for this purpose the 4 separate results obtained each night. 
As appears from these tables there is only one determination of 
time at Mecca (Febr. 26) which is not based on an eastern and 
