34 li. F. Rand — Angra Pequena 



The holes bored into the rock are usually more or less circular 

 in outline at the inlet, and burrow into the rock to varying depths. 

 The cavities worn are chambered out and frequently coalesce, 

 giving rise to cells and caves which are sometimes large enough to 

 shelter man. 



Should granite and schist have been rolled out into even, alternate 

 laminae, and the constituent minerals disposed in order, the holes 

 may be regular in size and lie in a straight line. If equidistant, 

 as they sometimes are, they may look as though drilled by human 

 hand. Sometimes the outlines are quadrangular, and the rows may 

 even suggest the pigeonholes in an office desk. There may be simply 

 smoothing and dull-polishing of such a rock, and should the layers 

 crop out vertically they show ridge and furrow, the harder granite 

 being in relief. 



Where there has been intimate admixture of felspar and schist 

 the more resistant felspar stands out in studs. The veins of felspar 

 also jiroject, but with their sides unsuj^ported the felspar is at the 

 mercy of its main cleavages and falls in fragments. High up upon 

 clifE-faces one may see holes which resemble those made by martins 

 in some hospitable sandbank. 



The granite varies very much in its resistance. Sometimes it is 

 deeply holed and cavernous ; sometimes it shells away in concentric 

 flakes ; sometimes it shows good resistance and is merely dull- 

 polished. 



The segregations of quartz are, as one would suppose, very 

 resistant. Such masses have their surfaces more or less polished 

 and lightly scooped out into shallow de]3ressions of varying size. 

 All salient angles are rounded off. There is a general smoothing: 

 over. Pitting, in quartz, when it occurs, is usually small and due 

 to the breaking down of small less-resistant inclusions. Yet the 

 foot of a quartz slope is littered with angular fragments, owing, 

 apparently, to the minute fissures and joints which traverse the 

 mass. 



Most of the holes one sees, whatever the nature or texture of the 

 rock, are driven more or less horizontally inwards, after the fashion 

 of adits, but holes are sunk downwards also. The chemical action 

 of the wind-borne salt and moisture, and the grind of the air-driven 

 sand and grit, sap at all vulnerable surfaces. As the holes deepen 

 they come more and more under the swirling effect and scour of the 

 rock-fragments, sand, and grit which they come to harbour. They 

 may be regarded as aeolian " pot-holes ". 



The lofty sides of the ravines and gullies have their rocks deeply 

 honeycombed and wind-bitten. Air-currents frequently course 

 up or down them with violence. The holes may face up or down the 

 ravine. Perhaps there are more which face downwards. Air- 

 currents in broken country are so capricious and so easily deflected 

 that there can be little rule. 



One has to see the large quantities of waste littering the surface 



