240 Geological Section of the Strata [May, 



yellow limestone and the sandstones; this bed is of considerable breadth : 

 both however dip to the east at a considerable angle ; and as the limestone 

 occurs to the west of the sandstones, the former may possibly dip under 

 the latter, and the series of formations of the narrow bed described in 

 my published paper, may be thus completed. 



F, a hill composed of the out-croppings of the quartz formation which 

 shews itself further west. Benauti is situated at the base of this hill. 



G. G. G. Quartz rock as described page 31. It alternates with H. H. 

 H. &c. which is the rock described as an imperfect variety of granite 

 rock. It has a porphyritic structure, and might almost be classed with the 

 porphyries. It is however indistinctly stratified. In travelling from 

 Benauti to Nakum, as far as the yellow limestones occurs, the surface 

 is generally covered with soil from which the limestone occasionally 

 protrudes ; but on passing the limits of this vast formation, a very nar- 

 row bed of a slaty argillaceous rock presents itself, and this is immedi- 

 ately succeeded by the quartz, which rises occasionally into craggy and 

 rugged hills, and the outcroppings of the highly inclined, and in many 

 situations almost vertical, strata of which are constantly observed. The 

 line of section traverses a hill : also composed of quartz. I, The separate 

 section, K. is an imperfect representation of a hill composed of quartz 

 which occurs to the east of Nakrum. The slope in the direction in which 

 the strata dip is abrupt and destitute of soil. In the opposite direction, 

 it presents a bluff rugged face and which rises abruptly from the slope ; 

 M. M .,theslope in this direction beingmore gradual. The hills at Nakrum, 

 which are also of quartz, exhibit something of a similar appearance : these 

 rise about 300 feet above the level of the plain. The bluff crag L occupies 

 the highest position of the ridges, and the hills slope on either side their 

 summits, presenting bare perpendicular cliffs, rising abruptly to the east 

 and west from the slopes, which last are covered with stunted trees. 

 From Nakrum to Mangarwdr the surface, for the first half of the dis- 

 tance, is usually covered with soil, from which occasionally protrude 

 the quartz and the granitic rocks ; H. H. $c. As we proceed west the 

 quartz becomes purer and more transparent. It frequently assumes a 

 nearly slaty structure, in consequence of minute plates of mica being 

 parallel to the stratiform structure. Thus far the surface is nearly level 

 It afterwards becomes very gently undulating, and the out-croppings of 

 the quartz strata are occasionally seen occupying the gentle swells. 

 This quartz now appears to alternate with or rather there occur inclos- 

 ed in its narrow beds of argillaceous schist, the quartz being the prepon- 

 derating rock till within about three miles of Mangarwdr, when the 

 argillaceous schists become more plentiful. At and near Mangarwdr 

 ■the argillaceous schists pass into and alternate with greenstone schist 



