rises to 100° in the shade, but in so dry a climate this is not unpleasant, and I felt less oppressed by this heat than I did in London the previous September. Moreover, in Kimberley, owing to the high altitude, the nights are always cool. The approach to Kimberley is deadly dull. The country is almost treeless, and the bare veldt stretches its level length, relieved only by distant hills on the horizon. THE PIPES OR CRATERS The five diamond mines or craters are all contained in a circle 3½ miles in diameter. They are irregularly shaped round or oval pipes, extending vertically downwards to an unknown depth, retaining about the same diameter throughout (Fig. 3). They are said to be volcanic necks, filled from below with a heterogeneous mixture of fragments of the surrounding rocks, and of older rocks such as granite, mingled and cemented with a bluish-coloured, hard clayey mass, in which famous blue clay the imbedded diamonds are hidden. [Illustration: FIG. 3. KIMBERLEY MINE. THE “PIPE.”] [Illustration: FIG. 4. SECTION OF KIMBERLEY MINE. To face p. 18.] The craters or mines are situate in depressions, which have no outlets for the water which falls upon the neighbouring hills. The watersheds of these hills drain into ponds, called pans or vleis. The water, which accumulates in these ponds during the rainy season, evaporates during the dry months, only one of them holding water throughout the dry season. The rocks which surround the craters are capped by red soil or calcareous tufa, and in places by both, the red soil covering the tufa. The diamantiferous breccia filling the mines, usually called “blue ground,” is a collection of fragments of shale, various eruptive rocks, boulders, and crystals of many kinds of minerals. Indeed, a more heterogeneous mixture can hardly be found anywhere else on this globe. The ground mass is of a bluish green, soapy to the touch and friable, especially after exposure to the weather. Professor Maskelyne considers it to be a hydrated bronzite with a little serpentine. The Kimberley mine is filled for the first 70 or 80 feet with what is called “yellow ground,” and below that with “blue ground” (Fig. 4). This superposed yellow on blue is common to all the mines. The blue is the unaltered ground, and owes its colour chiefly to the presence of lower oxides of iron. When atmospheric influences have access to the iron it is peroxidised and the ground assumes a yellow colour. The thickness of yellow earth in the mines is therefore a measure of the depth of penetration of air and moisture. The colour does not affect the yield of diamonds.