674 MR. G. E. SCOTT ELLIOT A.KD DR. J. W. GREGORY [Nov. 1895, 



epidiorite, but in some cases alteration has proceeded farther and 

 only a quartz-actinolite rock remains. In some places the rocks 

 are coarser in grain and are roughly foliated, and they then offer 

 some resemblance to the banded amphibolites which are such con- 

 spicuous members of the series of rocks of the Archaean plateau in 

 British East Africa. 



In the absence of more detailed information as to the field-rela- 

 tions of these rocks, we cannot prove conclusively their nature and 

 origin. But the petrographic evidence suggests that the different 

 varieties are all phases of one basic igneous rock altered by dynamo- 

 metamorphic agencies. 



Prom these rocks a long gradual slope, interrupted only by a cliff 

 at 5000 feet, leads down to the alluvium beside the Semliki at a 

 level of little over 3000 feet. 



(4) Volcanic Rocks on the Plain around Ruwenzori, 



It will be noticed in the sections previously described that no 

 volcanic rock of recent date has been met with. Stuhlmann tells us 

 that though it is naturally not impossible that one may find traces 

 of volcanic activity such as lava, tuff, etc., nothing of the sort has 

 yet been discovered. 1 Nevertheless, there is abundant evidence of 

 recent volcanic action on the plains at the foot of Buwenzori. Hot 

 springs occur in several places, though we attach no value whatever 

 to these. But the plains, especially to the east and south-east, are 

 studded with small volcanic cones : the most northerly of these is 

 at Yijonga, near Kasagama's. More than one of the cones contain 

 a small, deep blue crater-lake, and the specimens from it [96] are 

 a normal volcanic tuff. At Kyatwa is another circular lake, which 

 is probably a crater-lake, and the hill beside it is possibly the 

 remains of an old volcanic cone. The specimen of sand collected 

 from this [153] is composed of volcanic materials, but has possibly 

 been re-arranged by water ; another specimen, however, is obviously 

 a recent volcanic agglomerate. At Chukaronga is another crater- 

 lake ; between this and the shore of Buisamba are two more, and 

 at Katwe is yet another. Moreover, between Katwe and Chuka- 

 ronga runs a ridge of old Archaean rocks, including a foliated 

 epidiorite [166], which is capped in places by an olivine-basalt 

 [152], the appearance of which is very fresh. 



There is, therefore, no doubt that volcanic action has taken place 

 on the plain at the foot of Buwenzori, and both the persistence of 

 the craters and the freshness of the rocks indicate that they are of 

 comparatively recent age. These craters are arranged on lines 

 which radiate outwards from Buwenzori. 



1 Stuhlmann, ' Mit Eniin Pasha,' [1893] 1894, p. 298. 



