During Lower Old Red Sandstone times the district of Glen Coe furnished an arena wherein terrestrial disturbance and igneous activity combined to produce effects of imposing magnitude and, as we believe, of some theoretical importance. The paper now presented embodies an account of a cauldron-subsidence which affected an area roughly oval in shape, and measuring not less than 5 miles from side to side. We show that the subsidence took place in at least two stages, and that it was accompanied in a complementary fashion by the uprise of a series of marginal intrusions. In the first instance the nature of the volcanic succession in Glen Coe will be dealt with, its variations from point to point will be described, and evidence will be adduced to illustrate the marked inequalities of the floor of Highland Schists upon which these volcanic rocks accumulated. The second portion of the paper is devoted to the evidences of the cauldron-subsidence, and treats in some detail of its tectonic features and the accompanying plutonic intrusions. In a final section we have added a theoretical discussion of our results.