438 Major G. W. Williams— 



easterly portion of the Ningi massif are syenites and porphyries, 

 the latter predominating : small andesitic veins are found in the 

 porphyries and in the gneisses, but never in the syenites or Ningi 

 granites. North of the porphyries low outcrops of old granite are 

 sometimes visible (140). Passing westward along the northern edge 

 of the Ningi massif porphyries and rhyolites form the contact rocks 

 as far as Lumbo, but thereafter these intrusives thin out and the 

 contact with the old crystalline rock is obscured by superficial 

 drifts. Near Burra contact with gneiss is well defined. The 

 Ningi massif measures about 30 miles east and west, and averages 

 6 miles in width. The hills are rounded, and the highest points 

 attain an elevation of 2,850 feet. The granite is essentially a 

 riebeckite-biotite type, much more fine in grain than the ancient 

 Sabon-Garri type but similar in general composition. 



The Kila Granites. 



The Kila Hills rise abruptly from a level plain. The central peak is 

 probably about 3,300 feet in height. Although no contact rocks 

 are visible chilled margins (126) are to be seen towards the northern 

 edge of the hills. The granite is essentially a riebeckite granite 

 (124, 125). At Jugwa, near the centre of the massif, the riebeckite 

 forms large crystals up to 2| inches in length. The surface soil, 

 which is deei^ly banked in the valleys, is obviously mostly of eeolian 

 origin. North and north-east of the hills stretch the great plains 

 of Kategum, whose level surface of fertile wind-borne soil is unbroken 

 by hill or ridge. . 



The Fagam Granites. 



Travelling south-east from Kila to Guarani the route follows the 

 main Kano-Nafada-Lake Chad road. There is only one exposure 

 of gneiss and the soil is very deep. In a well at Yelua the water- 

 level was 37 feet. The soil was composed of alternate layers of fine 

 sands and marly clays, the latter probably of lacustrine origin. Near 

 Guaram rest-house are a few low ridges of syenite (129), and south 

 of the town numerous " floaters " of rhyolite and porphyry occur. 



Like the Kila Hills the Fagam granites rise abruptly from the 

 plains, and the deep soil is banked up the level-floored valleys and 

 against the northern sides of the massif. 



A few exposures occur about a mile from the hills : a biotite- 

 granulite (130) forms a cluster of boulders and near by the track 

 climbs steeply over an outcrop of quartz-syenite-porphyry (131). 



The massif itself is of considerable extent, and from a hill 2,500 feet 

 in height, which lies about 1| miles from the stockaded village of 

 Fagam, the granite can be seen stretching well away to the westward 

 of Gadama. The massif is composed of a somewhat coarse-grained 

 riebeckite granite (133). In places the riebeckite tends to form 

 bands (134). Pegmatite veins containing large riebeckite crystals 

 up to 2 inches in length were noted (135). Chilled margins and 



