Geology of Limerich. 37 



The older rocks include Silurian, referred to the Llandovery 

 division ; also Upper Old Red Sandstone, conformably overlain by 

 the Carboniferous, with which are included sundry volcanic rocks. 

 The greater portion of the area is underlain by the several divisions 

 of the Carboniferous Limestone series, comprising shales and limestones, 

 the latter in places oolitic, cherty, and dolomitic. The highest shale 

 division is grouped with the Yoredale Beds, and the overlying 

 flagstone series with the Millstone Grit. These strata were originally 

 classed as Coal-measures, but no coal appears ever to have been found 

 in them. The igneous rocks in the Limestone series are due to 

 contemporaneous volcanic action, and, although interbedded, Mr. Kilroe 

 believes that many of the lavas are intrusive in the tuffs and ashes 

 associated with them. Petrological notes are contributed by 

 Mr. Seymour. With regard to the physical features, it may be 

 mentioned that the Old Red Sandstone of the Cratloe Hills on the 

 north rises to a height of a little moi'e than 1,000 feet, and the 

 volcanic rocks of Knpckroe in the south rise to 672 feet. 



More detailed accounts are given of the superficial deposits, which 

 include Boulder-clay, Glacial Sand and Gravel, and Alluvial deposits. 

 To these descriptions Mr. Lamplugh contributes a general intro- 

 duction, and it may be safely averred that much of the work of his 

 colleagues is due to his inspiration. He has in fact left indelible 

 traces of his wide experience on Glacial phenomena in the several 

 Irish memoirs with which he has been connected. We learn that the 

 Boulder-clay is the direct product of an ice-sheet which invaded the 

 country in a general direction from north-west to south-east ; and that 

 while most of the included rock-fragments are local, yet with them 

 are occasional boulders of granite which may be traced to a parent 

 source on the north side of Galway Bay. 



The position and arrangement of the stratified glacial gravel and 

 sand is shown to be incompatible with marine agency, and it is held 

 to represent the material of the ice-sheet modified by fluvio-glacial 

 action. The greater part, if not the whole of the area, appears to 

 have undergone glaciation, but only the minor features have resulted 

 from this and subsequent action. Thus the Basin of the Shannon, 

 which, in the area of the map, extends from Castleconnell to Bunratty 

 and Mellon Point below Limerick, occupies a course that must be 

 regarded as essentially post-Glacial. Any pre-existing channels in 

 this area are concealed by the covering of Drifts. 



An interesting feature on the map is the indication of the general 

 characters of the soils on each subdivision, whether solid or drift. 

 To this subject Mr. Kilroe has given special attention, and it is 

 necessary to qualify the indications above given by his observations. 

 Thus he mentions that the boulder-clay, ' ' represented by one tint on 

 the map, is present in at least five distinguishable varieties, which 

 yield correspondingly different soils and subsoils." It would obviously 

 be impossible to indicate such minor changes on a one-inch map. 

 Other topics of economic interest are duly discussed, and the work 

 concludes with a useful bibliography. 



