Geology
The wet lowland of water-logged limestone known as the Hog of Alien stretches westward from New-bridge to beyond the Shannon. The bogs on it are a vast extent, though not continuous, and record the milder and damper climate that succeeded the dry epoch at the close of glacial times. The south-easterly trend of the depressions in which the numerous 
bogs of Longford and Westmeath have accumulated indicates a series of grooves determined by the ice-movement during the maximum glaciation. The hollows in the surface were first filled by lakes, which became converted by the growth of Sphagnum into bogs.
The soils of the area have been greatly influenced by the transport of limestone boulders from the plain into hollows of the mountains, and across the shales and sandstones of the flanks and the northern part of the up- land of the Leinster coalfield. Except where it is drift- covered, the Old Red Sandstone supports only a poor soil, suitable for heather and coniferous trees ; but the clays and loams on the adjacent Ordovician and Silurian tracts form arable land.
