5°2 
The Book of the Balance of Wisdom. [October, 
was a shining light. He was the author of a number of 
works on astronomy, cosmography, and physics, one of 
which entitled “ The Book of the Best Things for the Know- 
ledge of Mineral Substances,” and contained in the Ayin- 
Akbari, or Institutes of the Emperor Akbar, treats of the 
specific gravity of bodies and of hydrostatic methods for 
determining them. It is this work to which al-Khazini 
refers. A review of Abu-r-Raihan’s treatise has been 
published by Mr. J. J. Clement-Mullet, under the title, 
“ Recherches sur l’Histoire Naturelle et la Physique chez 
les Arabes.” * Since this Arabic manuscript is probably the 
most ancient work extant which systematically treats of 
specific gravities, we make another digression and give a 
brief synopsis of its contents. 
It contains theoretical explanations of the origin and for- 
mation of mineral bodies founded on the views of the Greeks, 
and particularly on those of Aristotle. According to these 
views, the variety of the weights of bodies depends upon the 
dry and the moist exhalation from them ; air and water are 
the elements of these vapours, air giving the lightness and 
water the heaviness. The author then proceeds to describe 
methods for determining the specific gravity of bodies in the 
following words :• — 
fr* “ Scientific men determine by means of water the measure 
of these differences in weights. They prepare a vessel filled 
with water in which they introduce ioo mithkals of each of 
the metals ; the quantity of water thrown out by each gives 
the difference in volume and weight, that one which dis- 
places the largest bulk of water has consequently the largest 
volume but the least density, and that one which displaces 
the least water is the heaviest.” 
Abu-r-Raihan gives in tabular form the specific gravity of 
nineteen substances, nine of which are minerals and nine 
are stones. In the following table we annex the values 
assigned by modern authorities, showing the remarkable 
accuracy, in most instances, of the early determinations : — 
Table of Specific Gravities. 
Gold . . 
Mercury . 
Lead . . 
Silver . 4 
Bronze ■ . 
bu-r-Raihan. 
Modern Authorities. 
i 9’°5 
19*30 
i 3 - 58 
i 3 ’ 5 68 
1 r '33 
11-346 
io ’35 
' 10-52 
8*8z 
8-05 to 8-95 
* Journal Asiatique. Serie v., vol. xi» 5 p. 379. 
