528 
oriental countries from 1803 to 1807 and in the latter year also 
visited Arabia and Mecca. His “Travels” were published in London 
in 18165). He made his astronomical observations with a reflecting- 
circle of 10inch diameter with 4 verniers by Troughton and an 
achromatic telescope by Dollond of 2'/, feet, with the aid of two 
chronometers by Brooksbanks and Pennington (see Vol. 1, p. XVII, 
Vol. 2, p. IX). The latitudes were determined by meridian altitudes 
of the sun and stars, the longitudes by the transporting of chrono- 
meters, by lunar distances and by observations of eclipses of the 
satellites of Jupiter. Of his determination of the position of Mecca 
it is mentioned in particular that it was accomplished by means of 
altitudes of the sun and of lunar distances (2, 94)’); in the meantime 
the chronometer by Brooksbanks had been broken, while probably 
shortly afterwards, that of Pennington was stolen at Mina in 
the neighbourhood of Mecca, so that the determinations of longitude 
could not be continued. Au Bey’s results, especially his longitudes 
such as they have been published can only be of little accuracy. 
Taking, however, into account the good instruments he had at his 
disposal, it is probable that a renewed calculation might amend 
matters, but his original observations are not likely to have been 
preserved. 
Besides from direct observations the position of Mecca might also 
be derived from that of Jidda by means of journeys between 
the two places with noted directions and distances, as the latter 
place has at present been accurately determined by the obser- 
vations of the English hydrography. Of these itineraries Hupur’s *) 
seems to stand first; it has been accurately calculated and discussed 
by J. J. Hess. Yet Hess*) himself must attribute to his results for 
the longitude and latitude of Mecca mean errors of resp. + 3’.2 and 
+ 3/8, 
So even after this last investigation the position of Mecca was very 
unsatisfactorily determined and Prof. SNouck HURGRONJE's proposition 
to try and obtain greater accuracy attracted me greatly. In the 
summer of 1909 I therefore applied to the director of the Leyden 
observatory, Prof. B. F. vaN DE SANDE BAKHUYZEN, who was much 
1) Travels of Att Bey in Morocco, Tripoli, Cyprus, Egypt, Arabia, Syria 
and Turkey between the years 1803 and 1807, writien by himself. London 1816 
2 vols. 
2) Erroneously J. J. Hess says in his Geographische Lage Mekkas that Aur 
Bry’s longitude of Mecca is based on eclipses of the satellites of Jupiter. 
3) CHARLES Huser, Journal d'un voyage en Arabie. Paris 1891. 
4) J. J. Hess, Die geographische Lage Mekkas und die Strasse von Gidda nach 
Mekka. Freiburg 1900. - 
