부산대학교 도서관

As a contribution to the study of magmatic differentiation, the author reports a discovery of quartz porphyry outcrops on the north shore of Lake Superior in which there are abundant globules of glass in a main mass consisting chiefly of glass. Evidence is submitted indicating that the globules were liquid at the time the surrounding rock was liquid, and that the two parts were of different composition. In all respects, the field occurrence corresponds to the description of the hypothetical case described by Bowen as being the only kind of phenomenon which would supply indisputable proof of the existence of immiscibility in silicate magmas. The unavoidable conclusion is reached that, if Bowen's criterion is correct, the occurrence of limited liquid miscibility in silicate magmas is a fact.