I. Introduction. At the request of the Council of the British Association, I undertook to examine the country in the neighbourhood of the Victoria Falls of the Zambezi River before the meeting of the Association in South Africa in the summer of 1905. Through the helpful cooperation of the British South Africa Company and the aid afforded to me by its officers in Rhodesia, I was enabled to make good use of the short time available to me for the task; and by rapid traverses of the wild country eastward of the Falls I gleaned much information regarding the geology and physiography of this little-known region. A preliminary account of the exploration was presented at the meeting of the British Association in Johannesburg, and has since been published in the ‘Report’ of that body. In this account the objects of the exploration and the circumstances of the journey are stated, and therefore need not be repeated here; but of the geological results it was only possible at that time to give a bare outline, pending the further examination of the material collected. My present object is to deal more adequately with the geological evidence. The traverses occupied seven weeks in July and August, 1905, during which time a distance of over 600 miles was covered, partly on the northern and partly on the southern side of the Zambezi, as shown on the sketch-map (P1. XVII), the area embraced within these traverses being over 2000 square miles. In exploration of