A Classification of some Rhyolites, Trachytes, and Phonolites from part of Kenya Colony, with a Note on some Associated Basaltic Rocks

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Abstract
In spite of the importance of the volcanic region of the Great Rift Valley of East Africa, very little attention has been paid in the past to the detailed petrography of the rocks of Kenya Colony. Previous work on the subject may be summarized in a few sentences. August Rosiwal described the rocks collected by L. von Hohnel on Count Teleki's expedition in 1886–88 (1891, pp. 490–511). Descriptions of some of the lavas of Mount Kenya were given by J. W. Gregory (1900) in his account of the geology of that mountain, which he ascended in 1893, and G. T. Prior (1903) described the rocks collected by Gregory in other parts of the Colony on the same expedition, and specimens from a collection presented to the British Museum (Natural History) by Sir H. H. Johnston in 1901. This paper contained five analyses. H. B. Maufe (1908) gave an account of the field relations of the rocks which he collected in 1905 and 1906 along the line of the Uganda Railway and on several traverses from various points along it. He followed Prior's nomenclature fairly closely. A few specimens collected by G. Uhlig, also on the line of the Uganda Railway, were described by M. Goldschlag (1912), who gave four analyses. Miss A. T. Neilson (1921) gave a brief description of the rocks collected by J. W. Gregory in 1919. Finally, A. Lacroix (1923) gave a short summary of the work of these earlier authors and added four new analyses of