107 The mode of occurrence and texture of this rock indicate that it is a flow, and not an injected type. In composition and texture it is decidedly of the bostonite type. The name bostonite has been used by Rosenbusch! for a dyke rock, but the type occurrence, at Marblehead Neck, near Boston, Massachusetts, is considered by some of those who are familiar with the locality to be an effusive and not an intrusive rock. In the absence of analyses, it seems best to designate the rock by the more general term trachyte, and to call attention to its bostonitic habit and probable composition. Where prospected, the trachyte is reported to carry values in gold. No free gold was seen and samples of the exposure were unfortunately lost. - The occurrence of this alkaline rock in the midst of a great basaltic series is analagous to the bostonite found in the Island of Skye.’ ORIGIN OF THE TERTIARY IGNEOUS ROCKS. The Tertiary igneous rocks of Graham island exhibit certain relationships that throw light on their origin, and on the history of the magma from which they were derived. These igneous rocks are naturally divisible into two series; the earlier Etheline intrusive rocks, and the later Masset effusive and explosive types. Some of the facts in regard to these Tertiary rocks are summarized below, and a discussion of them follows. In the intrusive rocks of the Etheline formation dacite has been found only as a dykerock, and never as a sill. Andesite forms both dykes and sills, the former in much larger number. Basalt has not been recognized in this formation, for all the basalt dykes that occur in association with it show marked affinities with the Masset rocks. The rocks of the Etheline formation are all highly altered types, differing in this respect from the Masset formation even more than their greater age would lead one to expect. The period of eruption of the Masset formation, which is almost 1 Rosenbusch, H., “‘Elements der Gesteinslehre,”’ 1910, p. 269. 2 Harker, A., ‘“Tertiary Igneous Rocks of Skye,” 1904, pp. 327, 289-290.