96 
Transadio7is of the Royal Society of South Africa. 
Addenda. 
1. O71 the term " MacW (see § 1). 
According to English and French dictionaries, the word is generally 
said to be French and to be derived from Latin macula — a spot. Now it 
is true that most macles of diamond are spotted ; but so are many well- 
shaped octahedra. Spots, indeed, are not by any means characteristic 
of macles, nor the most prominent feature. What is characteristic and 
prominent in macles is their shape and structure, so well expressed by the 
Dutch name " naadsteen " (seamstone). There is another French made, 
namely, the water chestnut (Trapa natans), and in this case the origin of the 
word has not been traced. Was d'Isle thinking of the latter when he named 
the former ? 
2. A Variation in the Size of Wesselton Diamonds, with Depth of Working 
(see § 2). 
It is curious that superimposed upon the irregular fluctuations of 
average size taking place from year to year, there appears to have been a 
definite increase in the average size of large Wesselton diamonds, i. e. in 
those of ten carats or more each. Also it takes a smaller yield now to 
produce a large diamond than it used to ; and the ratio of the weight of 
large diamonds to the total yield has increased. This is best shown in a 
summary, e. g., 
Years. 
Average size of large 
diamonds. 
One large diamond in 
Ratio of total weight 
of large diamonds 
to total yield. 
1898- 
1907- 
-1906 . 
-1917 . 
15'6 carats 
15-8 „ 
769 carats 
731 „ 
2-0 per cent. 
2-2 „ 
3. Cubes and Spheres (see § 6). 
Cubes of translucent and of opaque bort are fairly common in Bult- 
fontein, and of semi-translucent bort in Wesselton. Cubes of transparent 
diamond also occur, though rarely. The edges of the cubes are always 
much rounded. The indentations of the surfaces of some cubes tend to 
a square outline, giving an impression that the mass is built up of a 
multitude of tiny cubes, whereas the indentations of the surfaces of octa- 
hedra are mostly equilateral triangles in plan. Many cubes, as well as 
octahedra, are pitted with rounded holes (c/. § 12). An existing small 
yellow cube of transparent diamond shows internal strain. 
Spheres of translucent bort are called shot bort. Apparently the 
crystalline aggregates in these incline to a radial arrangement about a 
central nucleus which in most cases revealed by cleavage, if not all, consists 
of a discrete core of diamond or bort. 
