— Southern Nigeria, West Coast, Africa. 00 
truncated by one more acid; these occur also as streaks and irregular 
bands. Comparison of a series of specimens taken from a distance of 
about four yards demonstrates a passage between granite and gneiss, 
the only differences being distinctness in foliation and banding of 
the mica; texture and bulk composition remaining the same. 
The Granites.—Under this heading are placed all the later intrusive 
masses of acid composition, distinct from those grading into gneisses. 
They vary greatly in composition; doubtless they vary greatly in age. 
One of the best-marked masses in the Oban Hills ‘s the strikingly 
porphyritic rock of Itara. It is found near the word ‘ Huts’ (in the 
map of 1903), to the north of the village of Ikuri, and extends south- 
wards along the drainage basin of the Ukpong River, almost as far as 
Ibum. The rock is a biotite-granite, rich in quartz, and containing 
a multitude of crystals of pink orthoclase, occasionally a couple of 
inches in length. In a thin section the characteristic mica is of 
a yellowish-green colour; sphene and an epidote are common, and 
small crystals of apatite are not rare. The order of consolidation was 
apatite, sphene, epidote, biotite. Locally the rock is cut by aplite 
dykes. The typical granite of Ibum, near the headwaters of the 
Ukpong River, is a fine-grained, non-porphyritic rock containing 
sufficient biotite to give it a well-marked speckled appearance. Quartz 
is plentiful, and in places a suggestion of foliation may be noticed. 
About 15 miles north of the small river called ’Ndi ’Ncha, between 
{Ibum and Netim, I found a small boss of a rather peculiar granite. 
The rock is of a medium degree of ‘coarseness, characterized by blade- 
shaped and apparently homogeneous crystals of hornblende, scattered 
without orientation through the rock. Thin sections show these to 
consist of grains of green hornblende mingled with flakes of biotite. 
In some respects this rock, which has undergone a considerable amount 
of crush, is not quite a normal granite. Thus both ferromagnesian 
minerals enclose numerous grains of quartz or are greatly indented by 
them in a semi-poecilitic manner, the crystallization dates of the two 
minerals not being very different. Lobed outgrowths of felspar 
containing quartz vermiculé are also common. Microcline is absent, 
orthoclase predominates, although albite or oligoclase is abundant. 
Apatite is exceptionally plentiful, and one slide contains some 
interesting crystals and grains of white sphene. 
The granite forming the left bank of the Calabar River, one quarter 
of a mile above Uwet (now being quarried by the Public Works 
Department), is of a grey-coloured uniform rock of medium texture, 
practically devoid of hornblende or mica. The rock is composed of 
almost equal proportions of quartz and felspar; the latter includes 
orthoclase, microcline, and an acid plagioclase. Numerous small 
flakes of muscovite and occasionally granules of impure calcite are 
developed in the felspar, the former not seldom in considerable 
quantity. 
At ’Nsibimba, on the eastern side of the hills, is a very hard and 
massive biotite-granite containing rare garnets and muscovite; quartz 
and orthoclase are both abundant, and together build up practically 
the whole of the rock, for a triclinic felspar is exceedingly scarce. 
The rock has been only slightly modified by pressure. 
