IRELAND. 389 



enlarging their area, others grow smaller, and in the end disappear altogether, 

 although they receive the same amount of rain as before, and have not been drained. 

 Lakes of this kind are sucked up as it were bj^ the vegetation by which they are 

 invaded. Bogs, or wet spongy morasses formed of decayed vegetable matter, 

 cover hundreds of square miles in Ireland, and frequently occupy the beds of 

 ancient lakes, as is proved by the heaps of fresh-water shells found at their 

 bottom. In many instances this process of displacement is still in course of 

 progress. The lakes invaded by the marsh plants grow gradually smaller until 

 they resemble wells, dangerous to the wanderer unaware of their existence. 

 Occasionally, too, the spongy mass pours forth a stream of mud. This happens 

 after heavy rains, which cause the bog to swell, until its coarse tissue of vegetable 

 matter is no longer able to resist the pressure exercised from below. The gases 

 shut in beneath the upper layers of turf then escape with a noise resembling that of a 

 volcanic explosion, and streams of water and liquid mud rush out through the open- 

 ing effected by them. One of these eruptions took place in 1821 in the peat bog of 

 Kinalady, near TuUamore, about the centre of the great plain. Rumbling noises 

 had been heard for some time from the bog, and its surface heaved like an agitated 

 sea, when at length a torrent of mud, 60 feet in depth, burst from a crevice, 

 overwhelmed the houses and trees that stood in its way, and spread itself over an 

 area of 5 square miles.* Sometimes calamities of this kind result from a want 

 of foresight on the part of peat-cutters. By removing the peat from the neigh- 

 bourhood of a lake, the rampart which retains the still liquid mass that occupies 

 the interior is sometimes weakened to such an extent as to be incapable of resisting 

 the pressure from within, and an eruption of mud is the result. The history of 

 Ireland abounds in instances of this kind. The wanderer who wends his way 

 across the bogs can tell at once when he is passing over a concealed lake, for 

 the soil beneath him quakes with every step he takes, and he feels as if he were 

 walking upon a carpet stretched out in mid- air. 



The Irish bogs are amongst the most extensive in Europe, and even in the 

 vecnen of the Netherlands we do not meet with such wide tracts of almost 

 deserted country, where mud cabins as black as the peat in the midst of which 

 they rise are rare objects. The bogs of Ireland cover an area of 4,420 square miles ; 

 that is, nearly the seventh part of the whole island, and in many instances they are 

 40 feet thick. Those spread over the great central plain have an average 

 thickness of 26 feet ; but supposing the available peat throughout Ireland to have 

 a depth of no more than 6 feet, a reserve of fuel equal to 15,000,000,000 cubic 

 yards lies on the surface. Peat is largely used in the country for domestic purposes, 

 but cannot comj)ete with mineral coal in factories. 



The Dutch bogs naturally divide themselves into hooge veencu and laagc 

 vecnen, and similarly in Ireland we have red bogs and black bogs, according 

 to the plants of which they are formed and their degree of moisture. The black 

 bogs, which supply nearly all the peat, occupy the plain and the deeper valleys of 

 the mountains. The vegetable matter of which they consist is undergoing gradual 



* Jacob Noao-eratli, " Der Torf." 



