The Book of the Balance of Wisdom. 
5 I 5 
1876.] 
The temperatures at which the determinations of the 
“ hot water ” and “ sweet water ” were made are not known ; 
the difference of density observed — viz., 0*04166 — approxi- 
mates that between water at 3*9° C. and ioo° C., which ac- 
cording to modern physicists is equal to 0*04044. 
The high specific gravity of cow’s milk is noteworthy, and 
may have led al-Khazini and others into laCtometrical con- 
troversy. 
Besides these contributions to the knowledge of specific 
gravities, al-Khazini devotes some attention to certain sub- 
jects not closely connected with the main theme. In the 
third leCture he attempts to calculate the quantity of gold 
which would compose a sphere equal to the globe of the 
earth, and arrives at a number of mithkals which requires 
for expression 29 digits. 
In the same leCture he takes up the problem of the chess- 
board, of which he supposes the squares to be filled with 
dirhams, each square containing twice the number in the 
preceding ; he finds the total number of dirhams to be 
18,446,744,073,709,551,615. He then applies himself to as- 
certaining the dimensions of the treasury in which the 
treasure should be deposited, and finally quotes the lines of 
an Arabian poet which fix the time in which one might 
spend this sum at 200,000,000,000,000,000 years. 
In the last ledture he describes the methods of applying 
the balance to levelling and to the measuring of time. Of 
this portion M. Khanikoff gives the following concise expo- 
sition : — 
“ The balance level consists of a long lever, to the two 
ends of which were attached two fine silken cords, turning 
on an axis fixed to a point a little above its centre of gravity, 
and suspended between two sight-pieces of wood, graduated. 
At the moment when the lever became horizontal, the cords 
were drawn in a horizontal direction, without deranging its 
equilibrium, and the divisions of the scales of the sight- 
pieces corresponding to the points where the cords touched 
them were noted. For levelling plane surfaces, use was 
made of a pyramid with an equilateral triangular base, and 
hollow and open to the light, from the summit of which 
hung a thread ending with a heavy point. The base of the 
pyramid thus arranged was applied to the plane which was 
to be levelled, and carried over this plane in all directions. 
Wherever the plane ceased to be horizontal the joint deviated 
from the centre of the base. 
“ The balance-clock consisted of a long lever suspended 
similarly to the balance-level. To one of its arms was at- 
2 u 2 
