Odliquity of the Ecliptie. aA 
ANAB AND PERSIAN OBSERVATIONS. 
Mr. Caupin las been so good, at my desire, as to trams- 
Jate the part of Ebn-Jounts’ works which contains the 
Arabian observations. His translation is published in the 
7th volume of Notices of MSS. It contains the most nu- 
merous collection of Arabian observations; and among 
them, there are several relative to the ecliptic’s obliquity. 
There we see that in the year 214 of the Hegira, the astro- 
nomers of Almamon have observed at Bagdad the obli- 
quity of the ecliptic 23° 33’, and that three years after 
they observed it at Damas 23° 33'52". However, Ebn- 
Jounis relates the following passage, according to Ebn- 
haten-Alvvirizi. 
* The obliquity of the ecliptic of the astronomers of Al- 
mamon is the same as still continues in our times. Tt was 
observed by them with much exactness; and though they 
have not equally succeeded in their observations, owing to 
the knowledge they wanted, this last nas been very well 
made, on account of the magnitude and the goodness of the 
instrument, and of the little difficulty of the operation, and 
of the little help they had. This obliguity is 23° 35'.”” The 
Arabian astronomers appear to have gencrally confined 
theinselves to that determination ; but 1 find no other des 
tailed observations but those of Albatenius and Ebn-Jounis. 
In his work de Scientia Stellarum, ch.iv. Albatenius says: 
«* With an instrument formed of several sides and a very 
long cross staff, such as is described by Ptolomy i in his Alma- 
gestes, after having ascertained the instrument’s position as 
well as could be, I found in the town of Arache, that the 
smallest meridian distance of the san from the zenith was 
12° 26°; and that the greatest was 59° 36’. These two 
distances, corrected by the refraction and parallax, become 
12° 96’ 10", and 59° 37 32 Half their diflerence gives 
23° 35’ 41” for the ecl:ptic’s ‘obliquity, at the time of Al- 
batenius ; that is to say, about the year 881. The formulas 
of Méc. Cél. give for that epocha 23° 35' 13", which 
agrees reinarkably well with Albatenius’s observation.” 
” Here now is Ebn-Jounis’ observation, as extracted from 
ch. xi. of his work. 
** | have measured the greatest declination, and find it 
23° 35’, by making the parallax of the sun different from 
that given by Ptolomy, as I shall explain in this Table. I 
have found by the instruments of our Lord the Prince of 
the Faithful, Alaziz-Bellah-Nazar-Aboulmanzer, the sun’s 
altitude at noon, after being corrected by the parallax, which 
‘Be3 diminishes 
