SOI 
Geological Relations of the East of Ireland. 
of eddies, and opposite currents. There is scarcely any part of the 
extensive limestone tract that is not more or less marked by them. 
Sometimes these ridges appear like regular mounds, the work of art, 
forming a continued line of several miles in extent. That which 
passes by Maryborough, in the Queen’s county, is a remarkable 
instance of the kind ; and similar mounds, hillocks, and ridges occur 
also in the counties of Meath, Westmeath, Kildare, Carlow, and 
other portions of the limestone field, in which the calcareous gravel 
and sand frequently exhibit a stratified disposition , the alternate 
layers being very distinct from each other. 
§ 212. The inequality of surface thus produced seems to have 
occasioned the formation of those extensive tracts of peat bog, which 
cover so considerable a portion of the limestone plain of Ireland. 
The natural course of springs and streams being obstructed, stag- 
nant lakes and pools of water were created, thus promoting the 
growth of those aquatic mosses and plants, which by their constant 
successive accretion and decay, appear to compose the mass of the 
bogs of Ireland. In this manner, it is conceivable that shallow 
lakes may in process of time have become entirely filled with peat $ 
and that peat bogs may thus have gradually acquired a convexity 
of surface, or at least that greater declivity by which their borders 
are distinguished, according to the Reports of the Engineers em- 
ployed in surveying the bogs of Ireland. The average depth of 
these bogs is commonly from sixteen to twenty-five feet, but some 
reach from thirty to thirty-five feet, and the extreme depth observ- 
ed is forty-seven feet. In the same manner, we may conceive the 
gradual growth of peat bog to have successively extended from the 
higher regions to the flanks, and thence to the feet of mountains. 
That fallen forests were not the primary origin of these peat bogs 
