Yol. 6^.~] THE GEOLOGY OF THE OBAN HILLS. 315 



Taking this series (6) as a whole, proofs of contact-metamorphism 

 are abundant. At almost the lowest point of the Uwet Kapids is 

 an example of an exceptionally-fine Fruchtschiefer (spotted slate), 

 in which the prisms discernible on a weathered surface measure 

 occasionally 4 inches in length. 



The rock in which these growths oecur is a somewhat altered 

 slate, in which white mica has been abundantly developed. Some 

 of these metamorphic effects have doubtless been caused by the 

 intrusion of granites, for these rocks form both banks of the river 

 above Uwet Bungalow, almost as far as the lowest rapids, and are 

 met with again about 4 miles up stream. Some 2| miles up stream, 

 that is to the northward, occurs a staurolite-schist, and exceedingly 

 well-formed crystals of the characteristic mineral are found in the 

 pans taken from the gravels of streams between Ewen and Ekpri 

 Ibami, suggesting a wide distribution for this type of rock. 



The series varies considerably, both in degree of alteration and 

 in composition. Usually, the rocks are practically mica-schists; but 

 interbedded, as it would seem, with them is a second type of 

 compact bluish-grey rocks with conchoidal fracture, containing ill- 

 formed garnet, occasionally andalusite, and blades of an ortho- 

 chlorite. 1 Other rocks are distinguished by the occurrence of 

 tremolite. 



Study of the field-evidence and of the specimens collected seems 

 undoubtedly to show that the phyllites and grits which crop out near 

 the Uwet Bungalow, by contact-metamorphism become reconstituted 

 into mica-schists and hornfels in a distance of, say, 6 miles. The 

 strike of the altered rocks is so variable that too much reliance 

 must not be placed on any observed direction ; but, judging from a 

 number of observations, there can be little doubt that in travelling 

 from north to south we are working across and not along the strike. 

 So far as the investigation has at present gone, the phyllites and 

 grits are not seen again when we have once reached the area 

 occupied by the mica-schists, nor do gneissose rocks appear which 

 can be confidently determined as altered felspathic grits or grey- 

 wackes. I consider that between Uwet and Akwa Ibami we have 

 an example of extensive and far-reaching contact-metamorphism, 

 and it seems not a little suggestive that the banded sillimanite- 

 gneisses of the Ekankpa Ford are found only 5 miles north- 

 east of the typical areas of contact-metamorphism at Uwet and 

 Buden. 



Two other districts throw some light on the Uwet rocks : — 

 (i) Near Akpum, on the Xwa Hiver (a few miles below 

 Abu ton). — Two types of rocks have been collected and examined : 

 one appears to be an altered grit, the other approximates in appear- 

 ance to the green schists of the Alps and the Start. In neither 

 does any clear trace of an original constituent remain. 



1 Probably nearer to pennine than to clinochlore. 



