SUMMARY 
OF THE GEOLOGICAL OBSERVATIONS MADE IN 
UGANDA AND IN THE RUWENZORI RANGE 
DURING THE EXPEDITION OF H.R.H. THE 
DUKE OF THE ABRUZZI, 
BY 
ALESSANDRO ROCCATI. 
I.—UGANDA. 
Overlooking for the present the recent surface formations of concretionary 
limonite and of laterite, that part of Uganda which was traversed by H.R.H. 
the Duke of the Abruzzi’s Expedition was found to be for the most part 
-constituted of the crystalline rocks which form the archaean plateau of Central 
Africa. A not inconsiderable tract, however, of the region traversed is covered 
with sedimentary formations referable to the Palaeozoic Age, and in the inter¬ 
mediate neighbourhood of Fort Portal there is an apparently limited zone in 
which the crystalline rocks are overlaid by recent volcanic formations, 
represented by stratified tuffs which I take to be of subaqueous origin. 
Archaean .— On leaving Entebbe in the direction of the west, archaean 
crystalline rocks are followed from the shores of Lake Victoria nearly to 
Mitiana. Here begin to appear the palaeozoic formations, which, interrupted 
here and there by out-cropping coarse-grained granite and pegmatite, extend to 
within a few miles of Kasiba, where they suddenly disappear altogether, their 
place being taken by the crystalline rocks, which continue westwards without 
further break and thus constitute the whole of the Ruwenzori Range. 
The archsean rocks are represented by mica-schists, gneiss, and granites (always 
associated with numerous quartzites), amongst which are here and there noticed 
intrusive greenstones, and seams of pegmatite, microgranite, etc. 
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