444 Of the Bogs in Ireland. 



appear, according to the report which Mr. Griffith, jnn. 

 has made on the subject; wherein, p. 15 and 16, the tract 

 of land called the Island of Allen is thus described : — 



<c The surface of the Isle of Allen rises very quickly 

 from the bog on all sides, particularly to the north-west, 

 where it is composed (at least to a considerable depth) of 

 limestone gravel, forming very abrupt hills, in those places 

 where the face of the hills has been opened for the pur- 

 pose of raising stone and gravel, the mass is con-posed of 

 rounded limestone, varying in size from two feet in dia- 

 meter to less than one inch ; the largest are not so much 

 rounded as the small, frequently their sharp angles are 

 merely rubbed off; they are usually penetrated by contem- 

 poraneous veins of Lydian stone, varying in colour from 

 black to light grey; the colour of the limestone is usually 

 light smoke grey, rarely blueish black ; when it is, the 

 fracture is large conchoidal ; that of the grey is uneven, 

 approaching to earthy. 



" The Lydian stone, when unattached to the limestone, 

 has usually a tendency to a rhomboidal form, sometimes 

 cubical, the edges are more or less rounded, the longitu- 

 dinal fracture is even, the cross fracture is conchoidal. 



" From the strong resemblance that subsists between the 

 rolled limestone and its accompanying substances, and the 

 upper beds of the limetone strata, which extend from the 

 county of Tipperary, through Kilkenny, (where the lower 

 beds are used for marble,) Carlow, Queen's County, King's 

 County, Kildare, Meath, Westmeath, Dublin, &c. &c. 

 there can be no doubt that the least accumulation of lime- 

 stone gravel, which nearly covers the whole province of 

 Leinster (forming steep ridges of hills frequently above 300 

 feet high, and sometimes approaching the summits of lofty 

 primitive mountains) did originally form the upper beds of 

 the ljmetone strata, which when now found in situ are sel- 

 dom firm, on account of their alternating with thin beds of 

 slate, clav, usually much decomposed, and their being tra- 

 versed by numerous fissures and veins of calcareous spar and 

 Lydian stone. 



" It is much moredifficult to trace the course of the cur- 

 rents which first removed the limestone from its native bed, 

 and afterwards having rolled the detached masses backwards 

 and forwards, deposited them on the sides of hills, whose 

 base had withstood the action of the waters, or by cross 

 currents and eddies formed independent hills and minor 

 ridges, the deposition of which, together with a subsequent 

 deposition o.f a bed of clay, varying from one to six feet 



in 



