﻿316 ME. J. PAEKIXSOX OX THE PETEOLOGY [May 1908, 



but in one observed iEstance, where the Tuma falls into the St. Paul, 

 the remnants of a. hanging valley can be seen. 



Alluvial flats raised above flood-level are conspicuous in many 

 river-valleys. 



A line trending about 280° true, and passing a little to the 

 south of Boporo, near Horpa, and a town a short distance to the 

 north of Degbe, approximates to the southern limit of the hill- 

 country, and is not far removed from the coast-line in direction, 

 about 300° true. 



Flat-topped ridges and isolated hills, trending parallel to the 

 foliation of the gneiss, are characteristic of the country around 

 Sanoyei and Boporo. 



The hill-ranges near the former town, rising from the well- 

 marked peneplain on the south, are very clearly seen from the 

 country to the north of Kaka ; and at Boporo the successive ridges 

 forming the outlying spurs of the Po Eange are to me very sug- 

 gestive of successive terraces of marine denudation. 



A submergence of 700 feet would cover the southern part of 

 Western Liberia with water almost as far north as 6° 50' lat. X. 

 Throughout there is a striking absence of late deposits in the form 

 of old gravels and sands. 



EXPLAIS^ATION OF PLATE XXXV. 



Sketch-map of part of Western Liberia, on the scale of 16 miles to the inch. 

 (From surveys executed by Mr. S. M. Owen, A.R.S.M., and others.) 



DiSCESSIOX. 



The Peesident commented on the value of the communication as 

 to the nature, and more especially the strike, of this geologically 

 little-known region. Further details in respect to the haematite- 

 schists would be welcome ; they seemed to suggest the Dharwar 

 Series. 



Dr. J. "W. Evans referred to the fact that the Po and Boporo 

 hill-ranges were parallel to the strike of the crystalline rocks, and 

 enquired whether there was any evidence of such a variation in the 

 nature of the latter as would account for these features by differ- 

 ences in the rate of erosion. He remarked on the comparative 

 rarity of hanging valleys at low altitudes in the tropics, where 

 glacial conditions could not have affected the character of the 

 erosion. While admitting that the hanging valleys of the west 

 coast of tropical Africa might be accounted for by the rejuvenation 

 of the main streams due to the rise of the land relatively to the 

 sea, he thought that they might be the result of local variations in 

 the rainfall at a time when (as Avas not improbably the case) this 

 region was less well watered than at present. 



M. M. Alloege enquired whether the Author had found any 

 traces of the former extension of the Cretaceous sandstones in the 

 areas traversed bv him. 



