424 ME. A. J. C. MOLYTTEUX ON THE [Aug. 1909, 



blown away, or is removed by the first rainstorm ; and, sooner or 

 later, the pebble sinks downwards into the cavity formed by the 

 insect. And, as there is frequently a steep fall to the surface of the 

 ground, it moves onward. 



There is thus a progression in a downward and onward direction ; 

 and if we consider that the disintegration of the rock-mass took 

 place at as much as 1500 feet above what is now the valley-level 

 (there are remains of the conglomerate at the head of the 

 Muchinda Pass at that height), it will not be difficult to understand 

 how the shingle has crept downwards into the valley without the 

 aid of streams. Of course, storm-channels do help in the movement ; 

 but these shingle-mounds and sheets under the hillsides are mostly 

 unsorted, the fragments being of all sizes just as when liberated 

 from the mass. 



Another point is that the surface-shingle retains its peculiar 

 polish and shimmer in the sunshine, while pebbles to be found in 

 the river-courses are roughened and ' frosted ' by chipping together. 

 Again, no pebbles of normal gneiss and schist are found among the 

 derived superficial shingle. 



"We may return now to a description of the conglomerate in situ. 

 This outcrop extends along the foothills of the Lupoposhwe range 

 for a distance of 4 miles (that is, from Chigona on the east to the 

 Kalungushi on the west), and is generally visible in small creeks. 

 The Eakanunga is a V-shaped gorge cut down through the con- 

 glomerate and into the gneiss, which there dips steeply northwards. 

 The right-hand cliff slopes abruptly southwards ; and perched upon 

 the top is the conglomerate, with many dislocated blocks, showing 

 the unconformable contact. Masses of the rock fall into the creek 

 below ; and one such, 60 feet in circumference, is figured in this 

 paper (PL XXIII), in order to show the arrangement of pebbles 

 and the lenticular and fissile sandstone that may be found at 

 irregular distances in the deposit. 



At Chigona the conglomerate changes to an opaline grit, in which 

 occur a few subangular white quartz-pebbles. Presh fractures 

 show a beautiful rose-pink matrix around sharp angular fragments 

 of quartz of uniform size. The surface changes to pale greenish- 

 grey, and the rock flakes slightly — cutting through grains and matrix 

 alike. The cement changes on weathering to a whitish earth, and 

 this may be the reason why it is mistaken for kaolin, and why 

 certain Karroo opaline sandstones are looked upon as ' felspathic' 



On the opposite side of the Muchinda Valley — which corresponds 

 with the southern limb of the syncline — there is much shingle 

 along the foothills, including many boulders, and in positions that 

 indicate their origin in masses of conglomerate, now reduced. East 

 of the Rutente River are many blocks of it, lying on the shingle- 

 talus ; and up the hill-slopes I found small pieces in situ, adhering 

 to the jagged edge of the quartz-schist, which there strikes east 



