I landed at Madagascar in December, and, after a few days at Tamatave, proceeded to Antananarivo. After a fortnight's stay in the capital, I then started on my journey south-eastwards, and after six weeks' almost continuous travelling, I arrived at Fort Dauphin, the extreme south eastern corner of the island. Most of this route is over very well-known ground, and Messrs. Baron, Grandidier, Hildebrandt and others have very thoroughly described the character of the country. The first part of my journey was to Lake Itasy, which is about two days' journey west of the capital. This district deserves notice, as the geological structure is peculiar. I passed over two rather extensive basalt flows, which appear to be of rather recent date, though the absence of any overlying rock renders it impossible definitely to fix their age. On this basalt there is a distinct change in the vegetation. Lysimachia parviflora and a few other species are more common, and Clematis anethifolia, Kniphofia pallidiflora, and others appear almost confined to it. The whole district near Lake Itasy is volcanic ; the country is studded with small cones of scorise, rising (in the neighbourhood of the lake) out of a level, marshy plain? and one is tempted to assume that the lake lies in a hollow due to the subsidence of the land through volcanic action. From Lake Itasy I went to Mr. MacMahon's station at Bamainandro, and near here I saw the celebrated subterranean river. It is a very simple formation. The strike of the strata is east and west nearly, and the river, running in the same direction, has burrowed its way underneath a harder layer of rock, which latter has subsequently broken off in large boulders and covered the stream.