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Show 1891.] BRITISH CENTRAL AFRICA. 311 The fullest and most interesting account of the Geology of the Nyassa country is that given by Prof. Henry Drummond as " a Geological Sketch" in chapter viii. of his 'Tropical Africa,' published in 1881. This sketch embraces the whole of the country he traversed from the mouth of the Zambesi to the Tanganyika Plateau. A coloured map accompanying this sketch serves to indicate in a general way the positions of the rocks that have been recorded by others, or directly observed by Prof. Drummond himself. In this chapter the fossil Fishes found by the author are described in detail by Dr. R. H. Traquair. Quite recently Prof. Rupert Jones (Geol. Mag., Dec. 1890) has given fin account of the coal and the fossil shells which have been found near the N.W. extremity of Lake Nyassa. Starting from the mouth of the Zambesi, at a distance of about 50 miles from the coast, there is, according to Prof. Drummond, an ancient Coral-reef, which, although standing only a few feei above the sea-level, probably indicates a slight elevation of this part of the coast. About 20 miles further inland near Shupanga, and still only at a very slight elevation, sedimentary rocks were met with consisting of "a few thin beds of red and yellow sandstones and fine conglomerates." No fossils were found ; but these deposits are believed to be of the same age as the beds at the Cape, which are known as the Karoo formation (Lowest Mesozoic), which seems to extend as far north as Zanzibar and Mombasa. Beds of coal are said to occur far up the Zambesi, at a place called Tete, and are probably associated with beds of the Karoo age, which it is thought will be found to form a narrow belt fringing the plateau of the interior. A little above the junction of the Shire River and the Zambesi, the first hills of the plateau begin ; they vary in height from 100 or 200 feet to 2000 feet, and those examined by Prof. Drummond "consisted entirely of white quartzite," the only quartzite he saw in Central Africa. At the foot of one of these hills (Morumballa) there is a hot spring, described by Livingstone. Livingstone spoke of coal occurring about 2 or 3 days' journey N.W. of Morumballa, but Prof. Drummond, after careful search, could find no trace of coal in the neighbourhood, and is of opinion that a black rock (very dark diorite) which does occur, and in the distance looks very like coal, must have misled Livingstone. The great African Plateau, including the upper part of the Shire River and the greater part of the country surrounding the Nyassa Lake, as well as half the plateau between the Nyassa and the Tanganyika, consists almost wholly of granite and gneiss; the character of the rocks being remarkably uniform throughout the area. Volcanic rocks occur at several places along the Zambesi and also at the northern end of the Nyassa. 'About six miles S. by E. of Mount Waller, on the N.W. shore of Lake Nyassa, Mr. James Stewart noticed some coal occurring about a mile and a half from the Lake shore and about 500 feet above its |
