1876.] The Book of the Balance of Wisdom . 497 
And immediately following this passage, occurs mention 
of the date : 
“ I sought assistance from his beams of light irradiating 
all quarters of the world, and was thereby guided to the 
extent of my power of accomplishment in this work, and 
composed a Book on the Balance of Wisdom for his high 
treasury, during the months of the year 515 of the Hegira of 
our EleCt Prophet Mohammed— may the benedictions of God 
rest upon him and his family, and may he have peace ! ” 
This proves the treatise to have been written in the years 
1121-1122 a.d. At this period of the world’s history we find 
Arab philosophers cultivating literature and science, while 
the rest of Europe was just immerging from intellectual 
darkness. The religious world had scarce recovered from 
the intense excitement aroused by Peter the Hermit and his 
followers, who led the tumultuous rabble 600,000 strong 
towards the Holy City ; and priests, knights, and peasants 
were preparing with frantic zeal for a Second Crusade. 
Abelard and Heloise were names which afforded endless dis- 
cussions in the cloister and on the hearth. Science was at 
a low ebb, a century elapsed before Albertus Magnus and 
Roger Bacon exerted their influence ; and scholastic philo- 
sophy, attaining its loftiest height, swayed the intellects of 
the age. 
The authorship of the Book of the Balance of Wisdom is 
easily determined by the fortunate circumstance that the 
author names himself several times, “ but in so modest a 
manner as scarcely to attract attention ; instead of heralding 
himself at once, in his first words, after the usual expressions 
of religious faith, as Arab authors are wont to do, he begins 
his treatise by discoursing on the general idea of the balance ” 
and then simply remarks : “ Says al-Khazini , after speaking 
of the balance in general ,” and proceeds to enumerate the 
advantages of the balance which he is about to describe. 
Two other passages in the extracts furnished by M. Khani- 
koff satisfy the Oriental scholars who have examined them 
that the author is the self-named al-Khazini. 
Attempts to identify al-Khazini with individuals of 
historical fame have given rise to differences of opinion, but 
the weight of evidence is in favour of regarding him as the 
same with Alhazen, the Arab optician and physiologist. 
Alhazen seems to have been a native of Persia, and to 
have resided in Spain and Egypt, but of his biography little 
is known. He is especially distinguished for his demonstra- 
tion of the theory of vision, showing that the rays of light 
are reflected from external objects to the eye, and do not 
VOL, VI. (N.S.) ZT 
