578 Scientific Proceedings, Royal Dublin Society. 



amongst which the principal was that of Birre, a market town^ 

 otherwise called Parsons-town, after one Sir Laurence Parsons. 

 . . . From this place Dublin was furnished with all sorts of 

 window and drinking glasses, and such others as commonly are in 

 use. One part of the materials, viz. the sand, they had out of 

 England ; the other, to wit, the ashes, they made in the place, of 

 Ashtree, and used no other. The chiefest difficulty was to get the 

 clay for the pots to melt the materials in ; this they had out of the 

 North." 



LEITRIM. 



At the south-east of the county, margining Longford and 

 Cavan, also in a small exposure near Drumod, are Ordovicians, on 

 which reposes the Lower Carboniferous Sandstone. A small exposure 

 of Silurians, associated with Lower Carboniferous Sandstone, occurs 

 near Drumshambo, to the south of Lough Allen : adjoining that 

 lake there is a considerable tract of Coal-measures, a portion of 

 the Con naught Coal-field ; while farther northward there is 

 a small outlying patch of similar rocks to the south-west of Lough 

 Melvin. To the west, coming in from the Co. Sligo, is a ridge of 

 metamorphic rocks running north-east to and past Manorhamilton. 

 These rocks have been said to be Laurentian, but this is highly 

 improbable (page 517) ; and for the reasons given when describing 

 the Donegal rocks (page 548), it is probable that they are the 

 equivalents of the Arenig or Cambrian. 



Arenig (?) or Cambrian (?). — These rocks consist of green 

 quartzyte and other schists. None of the quartzyte is suited for 

 cut-stone purposes, but it may be used for flags, in rough work, or 

 for road metal. 



Ordovician. — Some of the grits and sandstones belonging to 

 this group seem not to be suited for cut-stone purposes, but locally 

 they are used for rough work. 



Silurian. — There is only a very small area occupied by these 

 rocks. Good stone can be procured in quantity in some places,, 

 but they are not sought after ; they are, however, used for local 

 purposes. 



Carboniferous. — In places, but especially in the south of the 

 county, the strata adjoining the older rocks are reddish or purplish 

 in colour, and range from conglomerates to fine sandstone. Some 



