Summarv of Geological Observations. 



It supplies the Inulding material adopted for the structures of ICuropeau 

 type at Entebbe, Mitiana, and other places. Its chemical composition is very 

 constant, containing a percentage of Fe 2O3, which varies from .51 to ')5 per 

 cent. ; hence it diflfers from that of the limonite nodules, which are found 

 in laterite, in which the percentage of Fe 20., may be as high as 82 per cent. 

 In this region the limonite forms several lising grounds, some over 300 feet 

 above the present level of the lake. As to its origin, I believe it was deposited 

 in the bed of the lake, at a time when it was far more extensive than at present, 

 as is evident from a whole series of indisputable facts, the decomposition being 

 effected by a mechanical process analogous to that which iti lacustrine basins 

 originates the limonite (bog ore) of marshy places. 



Hence, in my opinion, the concretionary liinonite may be of great 

 importance, as serving to indicate the former limits reached by Lake Victoria, 

 of which even Lake Isolt, near Bujongo, may be mei-ely a lemnant. Similarly 

 the few patches of concretionary limonite met in the Butiti di.strict may possible 

 represent old extensions of Lake Alliert. In the limonite are embedded 

 numerous stony fragments and nodules varying greatly in size. This detrita! 

 material is for the most part represented Ijy quartz, hyalitie (glassy), granular, 

 or jasproid. I rarely noticed nodides or fragments of gneiss, or of pahKOzic 

 rocks. So great at times is the abundance of (piartzose nodules or fragments 

 as to give rise either to conglomerates or else to breccias with linionitic cement, 

 as the case may be. 



The scenery of the limonite region is typical in the form of its rising 

 grounds. These do not present rounded contours, such as are normally 

 observed in other parts of L^ganda, but constitute elongatefl hills with levelled 

 summits, divided one from another by deep fissures, oi' else they stand isolated 

 on the plain, representing the remains of what at other times must have lieen 

 the unbroken surface of the ground. In this respect the Entebbe and .Mitiana 

 districts are characteristic. 



The Inti'rife resulting from the transformation of the felspar rocks, under 

 the action of the atmospheric agencies, aided by the high temperatiu-e and by 

 the alternating droughts and heavy rains, may be said to form the surface layer 

 of the ground throughout this region. It is found not oidy in the gneiss and 

 granite zones, Init also where the palaeozoic occurs and forms on the rocks 

 ill situ a covering of various thickness, which may in places acquire quite an 

 e.Kceptional development. Characteristic is always the inner red colour, which 

 is due to the excessive oxidation of the minicrous iron ores that we have seen to 

 be present in those rocks. 



In the laterite is often noticed an abundant micaceous hematite, which in 



385 2 C 



