1032 ‘ REPORT—1885. 
TUESDAY, SEPTEMBER 15. 
The following Papers and Reports were read :— 
1. Notes on a recent Examination of the Geology of East Central Africa. 
By Professor Henry Drummonp, F.R.S.H., F.G.S. 
The district traversed included the littoral belt at the mouths of the Zambesi 
and Quilimane rivers, the region watered by the Shiré river from its source in Lake 
Nyassa to its terminus in the Zambesi, the Shiré highlands, and the western shore 
of Lake Shirwa, the rock-basin of Lake Nyassa, and the southern portion of the 
Nyassa-Tanganyika plateau. The first geological feature, on entering the country 
from the Zambesi, was an ancient coral-reef studded with sponges, which is ex- 
posed on the Qua-qua river above Mogurrumba. A few miles further inland sedi- 
mentary rocks are reached at Mopeia. A poor section occurs in the Zambesi above 
Shupanga, the beds consisting of red and yellow sandstones with intercalated marls 
and fine conglomerate. No organic remains were discovered, but the section may 
belong to the series found in a similar relation along almost the whole coast from 
the Cape to Zanzibar and northwards. The first hills reached, at Morumballa, 
consist of a very white quartzite. A hot spring occurs here, and one or two others 
are found on Lake Nyassa. Of the coal which Livingstone mentions on the Lower 
Shiré no trace was found after repeated examination. Dark rocks, of intrusive 
origin, occur at the locality. The coal on the western shore of Lake Nyassa, dis- 
covered by Mr. Rhodes, and described by Mr. James Stewart, C.E., was visited, and 
found to be of inferior quality, and existing only in small quantity. The seven-foot 
seam described by Stewart was really composed of thin beds of alternately carbona- 
ceous and argillaceous matter. 
The whole country from the Shiré a hundred miles above its junction with the 
Zambesi, the whole Shiré highlands, the western shore of Lake Nyassa, and the 
plateau between Nyassa and Tanganyika for half its length, consisted, with 
one interruption, of granite and gneiss. The character and texture of this forma- 
tion persisted with remarkable uniformity throughout this immense region. The 
granite was an ordinary grey granite, composed of white, rarely pink, orthoclase ; 
the mica of the biotite variety. Sometimes the gneiss persists over a large area, 
sometimes the granite, while frequently the two alternate within a limited space. 
Associated minerals were rare. Intrusive dykes of dolorite occur on the southern 
border of the Shiré highlands above Katunga. The only volcanic rocks met with 
were those already described by Mr. Joseph Thomson at the north end of Lake 
Nyassa. The only break in the granitic series occurs on the north-west shore of 
Nyassa, near Karonga. On the Rukuru river is found a well-marked series of 
stratified rocks, consisting of thin beds of very fine sandstone and shales, and 
occasional beds of limestone. After considerable search these beds were found to 
contain numerous fossils, including fish, mollusc, and plant remains. These fossils. 
have not yet been examined, so that the age is uncertain, but the deposit is probably 
lacrustrine. Lake Shirwa is drying up rapidly, and there is evidence of a former 
and much larger Shirwa, which may have been confluent with Lake Nyassa. Lake 
Pomalombe is shoaling fast, and is the remains of a once greatly extended Lake 
Nyassa. Lake Nyassa lies in an immense rock-basin of granite and gneiss, the 
greatest depth being towards the high plateau on the northern end. A fter careful 
examination of this whole region no trace of glaciation, no houlder-clay, moraine, 
striation nor glaciated outline were anywhere to be detected. 
2. Report on the Rocks collected by H. W. Johnston, Esq., from the upper 
part of the Kilima-njaro Massif. By Professor T. G. Boxney, D.Sc., 
IL.D., F.R.S., Pres.G.S.—See Reports, p. 682. 
