I 



1835.] the Advancement of Science: 189 



country ; and, it is to this circumstance that the profusion 

 of ridges in Ireland is owing ; the depressions between the 

 the ridges becoming receptacles for water, and being after- 

 wards obliterated by the formation of peat, the result of the 

 decay of aquatic plants. 



It is, of course, beneath this accumulation of peat, and 

 in the subjacent marl that the remains of the Irish elk are 

 found. This marl is, in part at least, produced by the granite 

 previously described, and sometimes attains a thickness of 

 forty feet. 



The speaker then proceeded to consider the stratified 

 rocks ; first describing the primary tracts which occur to- 

 wards the coast, and then the vast and level district of 

 calcareous rocks which occupies almost the whole of the 

 interior of the island. The elevation of the strata through- 

 out Ireland is remarkably uniform, being N. E. and S. W. 

 in almost every part of the island; to this remark, however, 

 there are some exceptions, as, in the county of Tyrone, 

 where the elevation of the strata is from N. to S. 



From what has been stated, it is obvious that the primary 

 rocks generally occur near the coast, constituting the moun- 

 tainous regions of Down, Donegal, Mayo, Galway, and 

 Wicklow, &c. These regions containing all the usual primary 

 masses ; as gneiss, mica-slate, clay-slate, and quartz rock, 

 present in each locality many interesting appearances, 

 which we have not sufficient leisure to detail. 



Quartz rock, however, occurs at Dunmore Head, under 

 some interesting modifications. It contains abundance of 

 globular concentric concretions, differing, in no respect, in 

 their structure from the fibrous masses found in trap, and, 

 like them, decomposing in crusts. 



In Donegal, beds of primary limestone occur, often 

 alternated with mica slate, and have, in many cases, been 

 changed into dolomite. 



Mr. G. then remarked that his information concerning 

 the transition formations was less complete. These rocks 

 consist of the grey wacke and old red sandstone formations. 

 In Cove of Cork both these are schists containing fossils. 



These transition and schistose rocks are succeeded by the 

 mountain limestone, which occupies about two-thirds of 

 the whole surface of Ireland. The organic remains found 



