AbstractThe paper consists of two parts, both furnishing evidence that partially consolidated basalt can chill against penetrating acid veins. This recalls work by R. E. Wilcox on a mixed lava at Gardiner River, 1944. Part I is mainly concerned with certain composite intrusions where basic margins carry quartz xenocrysts and acid interiors carry quartz phenocrysts. It is argued that basalt magma rose from a deep source through quartz‐porphyry rock, melting and incorporating contacts. Presently the quartz‐porphyry melted bodily, and, no longer penetrable, followed its basaltic forerunner into the upper world. Being cooler than the basalt, it often appreciably chilled what it did not drive forward. Part II introduces some new features into the structural interpretation of the North‐West Belt of intrusions at Slieve Gullion, and claims that these intrusions and also the ring‐dyke of earlier date have been accompanied by marked distortion of country‐rock. The granophyre of the North‐West Belt seems to be essentially earlier than the associated dolerites. These latter melt the granophyre at contact and chill against rheomorphic veins. Much of D. L. Reynolds' work from 1937 onwards is accepted, including extensive remaking of Newry Devonian granodiorite under Tertiary conditions; but certain hypotheses of surface volcanitity and deep‐seated metamorphism a