KiNAHAN— Ow Some of the Irish Crystalline Iron Ores. 311 



No. 1. Lithomarge. — This is in part a methylotic rock, as it is 

 usually more or less steatitic. It probably consisted, at first, of 

 muds formed from tbe weathering of the exposed surfaces of the 

 dolerite, its constituents having been carried into the lakes by rain, 

 rivulets, and wind. In it there are beds and lenticular masses of 

 bole, sometimes rich enough to be worked as iron ore ; the normal 

 lithomarge representing the wash of continuous rains or the drift 

 of continuous or heavy winds, while the beds of bole may be the 

 wash after long periods of drought.^ In the lithomarge are blocks 

 of dolerite with the outer parts decomposed to a slight depth. As 

 these may occur at some height above the base of the lithomarge, 

 it is not very easy to account for their appearance. (See PI. svii.. 

 Scientific Proc, Roy. Dub. Soc, vol. iii., new series). This theory 

 for the formation of the lithomarge will not be received without 

 dispute. My son, Grerrard A. Kinahan, who has examined it very 

 carefully, believes that it cannot be a sedimentary rock, but that it 

 is evidently a methylotic dolerite formed in situ. In favour of this 

 theory he refers to the dolerite blocks in it, and the amygdaloidal 

 portions ; but apparently against this theory are the inlying beds 

 and lentils of bole, with thin seams and bits of Kgnite — the amyg- 

 daloidal portions are at the surface of the underlying dolerite flow. 



No. 2. Ochreous Rock. — This lies conformably on the Kthomarge, 

 forming its surface, and is called the pavement, because it is the 

 floor of the iron ores. The surface of the pavement has been 

 denuded. There seems to have been a break in the course of opera- 

 tions, as the measures above it were deposited under different con- 

 ditions to those below it. Before, however, describing the iron 

 ores (Nos. 3 and 4), we will turn our attention to the alumite and 

 lignite. 



Nos. 7 and 8. Alumite and Lignite. — These rocks, although placed 

 uppermost in the list, seem to be older than the iron ores, having 

 accumulated more or less contemporaneously with the lithomarge ; 

 they being littoral accumulating while the lithomarge was deposited 

 in the deeper water. The alumite appears to have been originally 

 lithomarge ; but as the bog (now lignite) extended out over the 



^ As in some cases, the lignite was forming at the margin of the pools, while the Litho- 

 marge was accumulating in the deeper portions.. It is prohahle that some of the iron 

 ore in these boles had its origin in the leaching by the Lignite of the colouring matter 

 from the lithomarge, as seams and pieces occur in the bole, but not in the latter. 



