76 
Transactions of the Royal Society of South Africa. 
E-yght as betwix adamauntes twoo 
of evene wyght, a pece of iren isette 
Ne hath no inyght to meve to no fro." 
{' The Parlement of Briddes/) 
And so in * The Eomaunt of the Eose.' 
Whereas 
" The dores were alle ademauntz eterne." 
('The Knightes Tale.') 
Grower uses "adamaunt" and "adamant" in our sense as "diamond." 
On the contrary. Shakspere uses the same word (' M. N. D.,' II, 1) in the 
sense of lodestone, although his "hard-hearted adamant" has a flavour of 
the diamond about it. 
The ' Oxford English Dictionary " has an interesting article on the word 
" adamant," and a number of quotations from English authors down to 
1750, which prove how little was known at first hand, or by experiment, of 
the properties of either lodestone or diamond. By many the adamant was 
thought to be a sort of natural opponent of the lodestone, counteracting the 
attraction of the latter for iron. Others regarded the adamant and lode- 
stone as identical, and thought that the diamond was the natural opponent 
of both. 
There is a good specimen of stewartite in the McG-regor Memorial 
Museum at Kimberley. The substance described by Wagner (p. 143) is, of 
course, not stewartite at all, but black bort, the same as, or allied to, the 
black bort mentioned in the previous section. 
8. Variation of Quality and Increase in the Output of Cleavages, 
WITH Depth of Working. 
The question is often raised whether the average quality of the diamonds 
found in the different mines deteriorates with working depth. It is a diffi- 
cult question to answer definitely, because the methods of winning the 
diamonds have improved with experience ; so that small diamonds which 
might have been lost twenty years ago are now saved, and hence that the 
average value must decrease. In other words, the proportion of good stones 
to bad must decrease even if the larger ones are as good as ever they 
were. In the table following are given for each year 1902-16 the relative 
proportions for Bultfontein of — 
(1) Stones— i. e. Close Goods, Irregulars, Spotted Stones, and Flats ; 
(2) Cleavages; 
(3) Rubbish and Bort; 
the mean working depth from which the diamonds were won increasing in 
that time from about 300 feet to 850 feet. The first column gives the years, 
the second the number of carats in thousands (M) sorted for sale, while the 
others show percentages of each class. 
