(402) 



EXPLANATION OF PLATES. 



Plate IV., Fig. 1. 



Case made of J-inch iron pipe, 3 J inches in outer diameter. At each end there 

 are iron rings which screw on, and into which the two end plates also screw. The 

 end plates are made to screw down tight on the lead with which the case is to be 

 tilled, and two screw plugs in the centres of the plates can be forced in tatake up 

 any spare space. Molten lead was first poured in to heat the case, and tipped 

 out directly it had set. The lead was then poured in to about half the height of 

 the interior ; a rod of hard shale and several limestone marbles were then placed 

 in position, and more lead poured in. Then more marbles were put in and the 

 case filled up. The lead was finally filed fiat, and the case closed by screwing 

 on the top. 



Dimensions before After 



Crushing. Crushing. 



Height Sjf inches 3— inches 



Outside diameter of pipe in centre Syg inches 4~ inches 



Plate IV., Fig. 2. 



The lead taken out of the case after the crushing and sawn in two, showing the 

 rod of shale and two marbles, the latter with no alteration of shape, but in reality 

 with vertical cracks not shown in the photograph. The markings on the shale are 

 original, and are probably due to rain-drips. It will be noticed that the rod is 

 cracked and forced outwards a little above the centre, or zone of maximum flowage ; 

 the cracked portion^ lies between two surfaces formed on the lead as the successive 

 pourings cooled. The foot of the rod is crushed to powder. 



Plate V., Fig. 1. 



Indented and crushed pebble of Ecca sandstone from the Enon conglomerate, 

 Nuy siding, New Cape Central Railway. 



Plate V., Fig. 2. 



Boulder of amygdaloidal melaphyre in the Glacial (Dwyka) Conglomerate, near 

 Prieska village, showing the splitting-up of the boulder into layers and shifting of 

 one of them. Photograph taken by Mr. A. W. Rogers from the boulder in situ. 



Plate VI. 



Long branching blowholes in melaphyre from the lavas of the Drakensberg in 

 the Division of Matatiele. The one on the right shows the actual bottom of the 

 lava-flow with the first cooled surface, then the zone of small vesicles, then 

 another solid zone, and finally the pipe amygdules. The white splotches on the 

 left-hand specimen are aggregates of felspar laths. 



