565 
2010m = 1'9"8 further eastward, hence: 
Longitude Jidda. Mecca-gate 39°12’34".8 = 2) 36m 505.32 
and consequently : 
Longitude Mecca Kabah 39°50’59".2 — 2h 39m 235.95. 
We have still attempted to find out the basis of Wuarron’s long- 
itude and whether the telegraphic determinations of the longitude 
of Aden and Suez have been employed for it. But although Rear- 
admiral C. J. pr Jone, Chief of the Dutch Dept. of Hydrography 
has with the greatest kindness put all the available charts and other 
data at our disposal, we have not succeeded in obtaining certainty. 
Direct data as to the basis of WHARTON’s longitude were not to 
be found. Then we tried to attain our end by consulting the charts 
of Aden, Suez and Alexandria and by comparing the longitudes 
given there with the results of the telegraphic determinations. ‘These 
had been executed principally in connection with the transit of Venus 
in 1874, and have been discussed by Airy *), CopELAND *) and Auwers *). 
We did not find any certainty in this way either, as in the first 
place it is not sure that the bases for the longitude in the different 
charts agree inter se, and moreover uncertainty as to the exact 
situation of the observation-spots prevented an accurate determina- 
tion of the longitude errors of the charts. 
Therefore it seemed impossible to find out with any probability 
the correction needed for the tongitude of Jidda adopted in the 
Adm. Chart. Consequently I must regard the longitude of Mecca as 
deduced above, as the most reliable value for the present. 
In order to find the total mean error of the longitude of Mecca 
from the meridian of Greenwich, we should have to know that of 
the adopted longitude of Jidda, and it is impossible even to estimate 
this. In the total mean error an unknown value 777 has therefore 
been included. 
Thus our final results for the geographical position of Mecca 
Ka bah become 
Latitude —+21°25'18'4 + 2"1 
Longitude 39°50'59"2 + W4' 4} + m7 
or 239" 233.95 + W(0-.29)' Hm; East of Greenw. 
1) G.B. Arry : Account of observations of the transit of Venus, 1874, Dec, 8. 
London 1881. 
2) Dun Echt observatory publications. Vol, Hf. Dun Echt 1885. 
5) A. Auwers: Die Venus-Durchgänge 1874 und 1882. Bd. 6. Berlin 1896, 
