432 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [May 24, 



base of extreme hardness ; it usually contains crystals of hornblende, 

 and occurs in regular layers of great thickness, some of which are 

 massive and break with a conchoidal fracture, while the others are 

 slaty and split vertically. It often occurs in isolated patches in the 

 vaUey and Unamara river. Although this rock has been called and 

 laid down on the map as quartz-porphyry, I should rather regard it as 

 an altered sandstone or quartzite, as by further investigation I found 

 the lines of stratification sufficiently distinct to justify such an in- 

 ference. 



Large dykes of gTcenstone occur, similar to those in granite, tra- 

 versing this formation, which extends to the Marakang river, where 

 it passes under an escarpment from the top of which sandstone like 

 that observed in the Mazuruni and Carubung has rolled down. At the 

 base of the hill a greenish bedded rock, dipping north, with green- 

 stone dykes and quartz veins, lies upon the conglomerate and white 

 quartzose sandstone, occupying in vertical height some hundreds of 

 feet ; and upon these are beds of considerable thickness of red and 

 yellowish sandstone ; the latter are slightly contorted. 



Continuing up the valley of Murap.ang the stratigraphical arrange- 

 ment is as follows : 



Grey sandstone in thin beds. 

 Yellow sandstone. 

 Pinkish sandstone. 

 White hard sandstone. 

 Conglomerate, dipping from .5° to 10° N. 

 Strike of the hill N.W. and S.E. 



Not far from the Karakanang river there are low rounded hills of 

 white and pink argillaceous sandstone, on the surface of which 

 quartz crystals occur in such quantity that they are called Crystal 

 Mountains. 



The mountain to the north-west of the village presents the fol- 

 lowing section : — 



150 feet of dark green slaty rock resting on granite. 



175 ,, red shaly sandstone. 



175 „ hard white quartzose sandstone. 



100 ., coarse pebbly conglomerate. 



200 „ pink and grey interbedded argillaceous sandstone. 



100 „ red ferruginous sandstone and beds of red jasper. 



The hills beyond the Karakanang river are formed of the white 

 argillaceous sandstone with small water-worn pebbles of quartz &c., 

 on which lie beds of hard red jaspideous sandstone. 



Beyond the Peepee river to the Cotinga a red thin-bedded sand- 

 stone occurs, containing red jasper; and at the falls of Orinedouke, 

 on the Cotinga also ; and from that to the pyramidical mountain of 

 Waetipu and Eoraima, the sandstone forms the surface-rock. 



"Waetipu mountain is composed of horizontal beds of sandstone and 

 conglomerate of a Kght yellowish or grey colour. Height estimated 

 at 5000 feet. 



Eoraima is a flat-topped mural mountain, rising to the height of 

 7500 feet above the sea, with perpendicular walls of 1500 to 2000 



