Published online by Cambridge University Press: 01 May 2009
New analyses are given of the Glen More Ring-dyke. The basic end of the variation diagram is found to differ considerably from that of the Normal Magma Series. The magma variation is explained by gravitative sinking of augite and iron-ore (and plagioclase), the olivine of the Normal Series playing only a subordinate part. Various objections are brought forward to the explanation of the magmas by hybridization. The peculiar microscopic aspect of the intermediate rocks is tentatively attributed to pneumatolytic emanations from the lower reaches of the column. It is shown that a gradual transition from basic to acid already existed before the final consolidation of the magma took place.