566 
The results obtained by J. Hess from the itinerary Jidda-Mecca were :') 
Latitude 21°21'.7 + 3'8 
Longitude 39°52'.5 + 3.2 
i. e. agreeing with our result within the given mean errors, which 
are still rather considerable. So we may conclude that by our 
work, the accuracy attained has been a great deal increased. 
Finally we shall compare our results for Jidda and Mecca with 
those of Ari Bry. The following are the corrections needed by the latter 
Ly A 
Jidda EE eye = 6' 35" 
Mecea = 2M 51” on 94! 4" 
EN 
Aut Bry’s errors in latitude are for both places about —3’; the 
errors in longitude are great and irregular, which need not surprise 
us, as they are the results from observed lunar distances (for the lon- 
gitude of Jidda also 2 observations of eclipses of Jupiter-satellites 
have been taken into account). Ara Bey also determined the latitude 
of a number of other places in Arabia. Perhaps these also need a 
correction of about —3’ and may then be fairly reliable. I dare not, 
however, decide this question here. 
8. Road from Jidda to Mecca. 
In this last paragraph I shall discuss the results obtained by 
Mr. Sarim in surveying the road between the two places, on a 
journey on foot from Mecca to Jidda, undertaken for this special 
purpose. This survey was made by means of observations with the 
boussole and by counting the steps. 
The boussole, of which mention has been made before, was a very 
handy little instrument by Casella, belonging to the Leyden observatory. 
It has a little telescope in which also the divisions of the azimuth- 
circle (full degrees) are made visible by reflexion. 
The following table contains the results of these observations and 
their further reduction. The road was divided into 92 parts, for each 
of which the direction and the length were determined. For the two 
terminal and 13 of the 91 intermediate points special names could 
be indicated in the first column. The 2°¢ and 3¢ columns contain 
for each of the parts of the road the direction @ read on the boussole 
and the length / expressed in steps. 
The directions « are counted from magnetic North to East, South 
!) Hess started from the following co-ordinates of Jidda, Mecca-gate : Longitude 
39° 11' 47" E; Latitude + 21°29'11", while the Adm. Chart Ed. 1905 gives 
39° 12’ 35"; + 21°29' 11”, Le. a longitude of 48” greater. 
