560 Scientific Proceedings, Royal Dublin Society. 



French chalk, carbonate of soda, oxide of manganese, fluor-spar, 

 and arsenic. 



" Ground granite was used formerly for the finer varieties of 

 glass, hut was discontinued in consequence of the high temperature 

 required for its fusion. Donegal sand was also used, and was 

 found very good ; but, owing to the price having risen, the use of 

 it was discontinued." 



FERMANAGH. 



To the north-west of the county there is a small tract of meta- 

 morphic rocks coming in from those of the Co. Donegal. They 

 are probably the equivalent of the Arenig, or perhaps Cambrian. 

 East of Lower (North) Lough Erne are Silurian of the " Lower 

 Old Eed Sandstone" type. The rest of the area is occupied by 

 Carboniferous rocks. 



The age of the Carboniferous rocks occupying the tract at the 

 south-east of the county, of which the highest summits are Slieve- 

 beagh (1255 feet) and Carnmore (1034 feet), is disputed. Griffith - 

 considered them " Calp," or the middle group in the Limestone ; 

 John Kelly, whose opinion is adopted by Dr. Hull, calls them 

 Coal-measures ; while Baily states the fossils prove them to be 

 Lower Carboniferous. As previously stated, we believe that they 

 are Coal-measures, and will refer to the lower sandstones as " Fer- 

 managh sandstone." (See Introduction, page 524.) 



West of Lower Lough Erne, extending S. S. E. from Lough 

 Erne, past Derrygonnell to the Arney river, is another tract of 

 Calp ; while north-east of Lower Lough Erne, in the Kish district, 

 the rocks are of the " Ulster Calp type," capped to the south-west 

 of Kish by a small traot of " Fermanagh sandstone" (Lower Coal- 

 measures) . 



In the western part of the county are Coal-measures, part of 

 the Connaught Coal-field, which, as previously mentioned, 

 extends into the province of Ulster. 



Ordovician. — The grits of this group can be used for walling 

 and rough purposes ; but, as there are usually better stones in the 

 vicinity, they are only very locally used. 



Silurian. — The sandstones, which are in the majority in the 

 mass, are generally shades of red, brown, and purple, although. 



