507 
1876.] The Book of the Balance of Wisdom. 
its length it bears a straight line crossed by small lines, by 
means of which we determine the weight of waters. One 
end is terminated by a cone, arranged in such a manner that 
the tube and the cone have the same base. This instrument 
is called haryllion . If you place it in water, point down- 
wards, it stands ereCt, and the divisions that cross the ver- 
tical line can be easily counted, and by this means the 
density of water is determined.”* 
Hoefer, the French Historian of Chemistry, in relating 
this statement, remarks that none of the commentators of 
the Letters of Synesius were able to explain the nature of 
this instrument until the mathematician Fermat, in answer 
to Castelli’s request, communicated his view, correCtly ap- 
prehending the principles and uses of the instrument 
described. This was in 1628, and now we learn that the 
Arabian philosophers five centuries earlier were perfectly 
Fig. 3. — Balance of Archimedes. 
familiar with the identical instrument mentioned by 
Synesius. 
Al-Khazini describes* several forms of balances at great 
length, giving details of construction and employment. 
One of these balances he ascribes to Archimedes ; and he 
professes to quote the particulars respecting it from Mene- 
laus, without however giving the title of the latter’s work. 
Another balance described by our author is that of 
Muhammed Bin Zakariya of Rai ; it differs from that of 
Archimedes by the introduction of the needle, called by the 
Arabs the “ tongue,” and by the substitution of a movable 
suspended bowl for the movable weight. 
Finally, in the fifth lecture, he gives a minute description 
* Synesius Opera, Epist* XV., Lutetia, 1612, 410, p. 174. 
