363 
EUCLID 
their way to Arabia. The Caliph al-Mansur (754-75), as the 
result of a mission to the Byzantine Emperor, obtained a copy 
of Euclid among other Greek books, and the Caliph al-Ma’mun 
(813-33) similarly obtained manuscripts of Euclid, among 
others, from the Byzantines. Al-Hajjaj b. Yusuf b. Matar made 
two versions of the Elements, the first in the reign of Harun 
ar-Rashid (786-809), the second for al-Ma’mun; six Books of 
the second of these versions survive in a Leyden manuscript 
(Cod. Leidensis 399. 1) which is being edited along with 
an-Nairizi’s commentary by Besthorn and Heiberg 1 ; this 
edition was abridged, with corrections and explanations, but 
without change of substance, from the earlier version, which 
appears to be lost. The work was next translated by Abii 
Ya'qub Ishaq b. Hunainb. Ishaq al-Tbadi (died 910), evidently 
direct from the Greek; this translation seems itself to have 
perished, but we have it as revised by Thabit b. Qurra (died 
901) in two manuscripts (No. 279 of the year 1238 and No. 280 
written in 1260-1) in the Bodleian Library; Books I-XIII in 
these manuscripts are in the Ishaq-Thabit version, while the 
non-Euclidean Books XIV, XV are in the translation of Qusfa 
b. Luqa al-Ba'labakki (died about 912). Ishaq’s version seems 
to be a model of good translation; the technical terms are 
simply and consistently rendered, the definitions and enun 
ciations differ only in isolated cases from the Greek, and the 
translator’s object seems to have been only to get rid of 
difficulties and unevennesses in the Greek text while at the 
same time giving a faithful reproduction of it. The third 
Arabic version still accessible to us is that of Nasiraddln 
at-Tusi (born in 1201 at Tus in Khurasan); this, however, 
is not a translation of Euclid but a rewritten version based 
upon the older Arabic translations. On the whole, it appears 
probable that the Arabic tradition (in spite of its omission 
of lemmas and porisms, and, except in a very few cases, of 
the interpolated alternative proofs) is not to be preferred 
to that of the Greek manuscripts, but must be regarded as 
inferior in authority. 
The known Latin translations begin with that of Athelhard, 
an Englishman, of Bath ; the date of it is about 1120. That 
1 Parts I, i. 1898, I, ii. 1897, II, i. 1900, II, ii. 1905, III, i. 1910 (Copen 
hagen).