78 Transactions of the Eoyal Society of South Africa. 
Whether any of this result is due to psychological reasons is hard to say. 
Diamond coloration merges from one class to another not by steps but 
imperceptibly. And it might therefore be plausibly urged that some 
cleavages which formerly were not brown enough to be called brown are 
now so called ; or that it is likely that improving markets have to some 
extent justified the promotion of individuals from the rubbish into the brown 
cleavages. Neither alternative has any trustworthy evidence in its favour, 
and my own impression is that the increase in the brown cleavages is real, 
the small deviations from a uniform increase showing no definite relation- 
ship to the deviations of rubbish and bort. 
The next table gives similar information for Wesselton for the years 
from 1898 to 1916 — namely, the relative proportions of — 
(1) Stones — i.e. Close Groods, Irregulars, Spotted Stou'^s, Browns, 
and Flats ; 
(2) Cleavages; 
(3) Rejection Chips, Rubbish, and Bort ; 
the mean working depth from which the diamonds were won increasing in 
that time from 125 feet to 800 feet. 
Table Showing the Percentages of each Class of Diamonds from the 
Wesselton Mine. 
Year. 
Carats sorted. 
Stones. 
Cleavages. 
Rejection el 
rubbish and 
M. 
Per cent. 
Per cent. 
Per cent. 
1898 
378 
31-72 
17-06 
51-22 
1899 
447 
29-53 
15-47 
55-00 
1900 
308 
28-14 
15-51 
56-35 
1901 
484 
28-08 
16-33 
55-59 
1902 
541 
26-65 
17-76 
55-59 
1903 
580 
25-97 
17-86 
56-18 
1904 
612 
23-86 
19-20 
56-93 
1905 
567 
24-98 
19-39 
55-63 
1906 
590 
24-41 
20-56 
55-03 
1907 
472 
26-81 
23-67 
49-52 
1908 
397 
25-95 
23-86 
5019 
1909 
618 
25-56 
24-72 
49-72 
1910 
525 
25-81 
25-61 
48-57 
1911 
409 
24-39 
23-43 
52-18 
1912 
522 
2417 
24-87 
50-96 
1913 
602 
23-05 
25-20 
51-75 
1914-16 
634 
23-38 
23-05 
53-57 
