Around Limerick (Self Catering, Limerick, Ireland) and extending south-eastwards for some 20 miles is a large area in which is displayed abundant evidence of volcanic activity during Car- boniferous times. The lavas and ashes have resisted the action of the weather better than the limestone which envelops them, and thus they form a series of low hills which are rendered conspicuous because of the flatness of the surrounding country. The old castle of Carrigogunnel, 5 miles west of the city, stands on one of these igneous masses. Caherconlish is another large exposure, whilst about Pallas Grean and Herbertstown they are developed in an almost continuous zone. The Carboniferous rocks may be divided into four groups. Given in order, the earliest being below, they are :
