1836.] a Turkish work on Navigation. 443 



the ascension, P^v and descension kUas- J ! f the stars. For exam- 

 ple, if you go north and make the star i^T^?-, eight edm; it is ele- 

 vated one inch : and if you go south, it is by eight zdms, one inch depress- 

 ed ■"• sr **• This is the whole section on the measure of the f'j (plural, 



? ' j \y ) an explanation which, however, helps me not a hit to understand 

 the true measure of a edm, in the reckoning of the ship's course so fre- 

 quently employed in the subsequent chapters. Nor have I been able to 

 obtain any explanation from our astronomers." 



We will now venture to offer the explanation which has occurred to our- 

 selves from perusal of the present translated chapter of voyages, and the 

 above extract conjointly. 



1. The earn, in practical or vulgar parlance, is said to be the eighth 

 part of the day and night. This, doubtless, applies to the nautical division 

 of the twenty-four hours into 8 watches, generally prevailing among ori- 

 ental nations, and exactly corresponding with the 8 pahars of the Hindus*. 



2. Again, the earn is seen above to be the eighth part of the ordinary 

 inch or issabd ; as the jo, or yava of the Hindus, is the eighth of their 

 angul : and the line of Europeans is the eighth of their inch : it is, in fact, 

 the vulgar subdivision by two and two, both of the unit of measure and 

 of time. Perhaps, indeed, edm may be a mere corruption of jo. 



It would seem, that to suit ordinary capacities, both the issabd and the 

 zdm had been transferred to the arc of the rude quadrant or astrolabe 

 used by the Arab seamen, in lieu of the more scientific division into de- 

 grees and minutes. Or it is very possible that in still ruder times the al- 

 titude of the polar star above the horizon was actually measured by fin- 

 gers' breadths, the hand being held out at the natural arms' length in 

 front of the face: for the measure of the arc thus subtended would nearly 

 agree with the value of the issabd derived from other considerations. 



The actual value of the issabd in degrees and minutes may be readily 

 found from the latitudes, or polar altitudes, of known places extracted 

 from Si'di's work. Thus the elevation of the pole Cape Guardafui is 

 always quoted at.4| inch; while at Jedda it is called 10 inches ; differ- 

 ence, 5| inches. The difference of latitude by our mode of reckoning is 

 21° 28'— 12°, 00'= 9 9 28'; which gives nearly 1°37' for the issabd or 

 inch. Now, as before stated, we were informed by an Arab Muallim that 

 the earn was 12 of our minutes, or 5 earns =■ 1 degree. Therefore, 8 earns 

 or 1 issabd should be equal to 96' ; or 1° 36', — so close an accordance 

 with the foregoing result, as to leave no doubt of the value of the issabd 

 and earn being 96' and 12' respectively on the celestial arc. 



It still remains to explain the divisions of the lower arc of their rude 

 instrument, and the kids, or point at which the readings of the upper and 

 lower index coincide, as also the point whence the divisions commence on 

 both quadrants, or what may be called their index error. 



* The subdivision of the pahar into eight gharis, is like the " eight bells" inta 

 which our nautical watch is counted off. 

 3 m 2 



