1 84 1.] Description of a Persian Astrolabe. 773 



intelligible the inscriptions on the Astrolabe, it were superfluous here 

 to enter into. 



I shall now take leave of this part of my subject, with the hope, that 

 a structure so laboured and unsubstantial, so carefully repaired and 

 sustained by selfishness and priestcraft, will at no distant date crumble 

 into dust, when the congenial shade of ignorance, which it now enjoys, 

 shall have been dissipated by the sunshine of knowledge. 



Geography. — I shall now describe the geographical and devotional 

 parts of the instrument. The association of these two subjects in one 

 category may at first sight appear singular, but it is none other than what 

 the Astrolabe itself exhibits. I have not deemed it necessary to present 

 a drawing of that part of the instrument exclusively devoted to these 

 subjects, since I feel reluctant to increase the number of the plates 

 beyond what is indispensably requisite ; and in the present case, I have 

 hopes of making myself understood by explanation alone. 



The bottom of the recess in which the Planispheres repose, is di- 

 vided by concentric circles, the common centre of which is the reason 

 of the recess into the annuli. The outer of these contains symbols 

 indicating the directions, generally expressed, of Mecca, from the places 

 named in the annulus next below, and correspond with S. E. for 

 South-East, &c. The second contains several of the principal places 

 of Mahomedan veneration and power, beginning, of course, with Mecca. 

 The third and fourth are devoted to the longitudes and latitudes of 

 those places respectively, and the fifth is occupied with the azimuths 

 of the Kaaba at each of them. The remaining annuli are similarly 

 occupied ; and thus by this neat arrangement, fifty of the principal 

 Mahomedan cities in Asia, with their absolute and relative positions, 

 are exhibited at one view. It must be confessed, however, that these 

 latitudes and longitudes are, with a few exceptions, under the most 

 favorable view of them, exceedingly inaccurate, and consequently, 

 so are also the azimuths dependent upon them.* Such places as 



* The following is their method of deducing the azinauth from the latitude. Having 

 cut off from the meridian, beginning at the zenith, an arc equal to the sum or differ- 

 ence of the latitudes, and from the prime vertical an arc equal to the sum or difference 

 of the longitudes, and from the points of section having drawn perpendiculars to the 

 arcs ; the point in which these perpendiculars meet is the zenith of Mecca. Then 

 having drawn chords to the arcs denoting the distances of the zeniths, and those ex- 

 pressing the differences of latitude and longitude, they easily obtained, by Plane Tri- 

 gonometry, the azimuth angle. 



