268 GEOLOGY OF BENIN AND ANGOLA 



fcioiis, I have only time to say, that the valley of Accra is 

 about 12 miles in breadth, and 50 miles in length ; the 

 bottom is covered with a soft sandstone, and this sandstone, 

 in one place, was obser^'€d resting upon clay-slate. The 

 mountains forming the sides of this long valley, as far as I 

 could observe, appear composed of quartz rock and clay- 

 slate, alternating vnth e-ach other, and disposed in strata 

 ranging S.S.W, and N.N.E., the dip from 30° to 90° (the 

 direction of the dip not mentioned). The quartz rock con- 

 tabis grains of gold, as I ascertained by careful examination. 

 In some blocks of rock {syenite) I noticed a good many crys- 

 tals of sphene, and in one place saw what I considered to 

 be black manganese ore. It is very hard and heavy, and 

 is fashioned by the Ashantees into balls. The cover of 

 alluvium, in the bottom of the valley and extending down to 

 the seacoast, is of such a nature as to lead me to conjecture 

 that it is of marine origin, and, therefore, that the sea for- 

 merly extended a long way inland. The bases of the hills 

 are richly clothed with trees ; but these diminish in num- 

 ber towards the coast, where there occurs only a bush here 

 and there." 



The occurrence of gold in the quartz rock, as ascertained 

 by Mr. Park, is a very interesting observation, as it allows 

 us to infer that probably much of the gold collected in 

 Africa may have been derived originally from this kind of 

 rock, which, in its broken down and disintegrated state, 

 may have formed the sands and gravels in which gold dust 

 is generally found. 



In Benin there are mountains (those of Cameroon on the 

 seacoast) said to be 1-3,000 feet high. The Congo district, 

 through which the Zaire flows, was examined for some dis- 

 tance up the river. The rocks met with were granite, 

 syenite, primitive greenstone, gneiss, mica-slate, clay-slate, 

 and primitive limestone or marble. 



The kingdom of Angola contains salt pits, from which 

 are extracted large slabs of solid rock-salt. According to 

 Battel, beds of rock-salt, three feet thick, extend over a con- 

 siderable part of the province of Dembea. 



The mines of Loongo and Benguela furnish good iron. 

 Copper and silver ores are said also to occur in Angola, 

 particularly in the kingdom of Majomba. There are alva 

 some considerable mines of copper in Anziko. 



