﻿314 ilE. J. PAEKIXSOX OX THE PETEOLO&Y [^a}' I908, 



rock. Closely related to the last is a specimen collected between 

 the Koi Falls and Stanley Wharf ; the hornblende is replaced by 

 hypersthene. To the north-west a magnetite-hypersthene- 

 rock is iound associated with acid gneisses and hornblende- schists 

 in the neighbourhood of Meant Barclay, and a related rock occurs 

 near Gwela and Eomde to the north of that hill. 



In the northern part of the district various types of biotite- 

 gneiss and hornblende-schist form the Po Eauge ; which 

 is, with its subsidiary ridges, the watershed between the Lofa and 

 St. Paul Elvers. The variation will be shown by the following 

 types collected in situ from the bed of a single stream, itself of 

 no great dimensions. They are a massive hornblende-gneiss, a 

 streaky semi-porphyritic gneiss with laminae rich in hornblende, 

 a hornblende-gneiss of finer grain than either of the above, a 

 biotite-gneiss, and a rock indistinguishable in a hand-specimen from 

 a granite. 



The rocks from other parts of the Kange visited by me do not 

 greatly differ from these, although some biotite-gneisses from the 

 western slopes are rather coarser in grain, and contain phenocrysts 

 of a pink orthoclase. It is noteworthy that gneissose veins may be 

 seen clearly transgressing the foliation of the hornblende-schists, 

 and are thus shown to be on the whole later in date. 



A prevalent east-and-west foliation (magnetic) distinguishes the 

 rocks north of the Arthington-Whiteplains area, and is apparently 

 correlated with lithological variations. 



The probable igneous origin of many of these gneisses and 

 associated rocks is suggested by an exposure at Yon on the St. Paul 

 River, where a coarse quartz-felspar vein of pegmatoidal habit cuts 

 clearly across the foliation of the biotite-gneiss, but is apparently 

 an integral part of the complex. 



Among the various members of this complex, however, certain 

 rocks were found which have the appearance of sediments : thus, on 

 the banks of a stream some 3 miles north of Bomboma, hsematite- 

 schists occur; they consist of quartz and hfematite, usually in 

 alternating laminae. Unfortunately, time did not allow of the 

 relations of these rocks to the surrounding gneisses being ascer- 

 tained ; but Mr. Byrde tells me that he has found similar rocks to 

 the north of the Basa country, and it is possible that we have in 

 them part of the schist-series of Arthington and Whiteplains. 



The remainder of the district, and this is by far the greater 

 part, consists of acid gneisses in which biotite is usually the 

 sole ferroraagnesian mmeral, and microcline is common. These 

 rocks are often slabby in habit, the quartz having a marked 

 tendency to form strealvs and lenticles. Garnets are of rare occur- 

 rence. Later granites and pegmatites are absent, but a specimen 

 which is practically a pegmatite has been forwarded by Mr. Byrde 

 from the Basa country. 



