238 Scientific Proceedings, Royal Dublin Society. 



feet long. This stone, like others of the same class, becomes a little 

 discoloured at first, but subsequently freshens to a bright green. 



Columbkill Lake, eastward of Millford. — A dyke at the north end 

 of the lake. Grreen ; fast colour; fine-grained; durable ; dresses easily 

 and well on any face ; can be raised of fair scantlings ; capable of 

 long and heavy bearings. The quarry was opened to procure 

 quoins, sills, window-stools, window-heads, while building the 

 Hospital at the Milford Workhouse ; since then it has remained 

 idle. 



Stone more or less similar to that at the Columbkill Lake dyke, 

 but generally more bedded, occurs in other places in that neigh- 

 bourhood, as also west of Mulroy Bay, and near Letterkenny. 



Wood quarter, N.W. of Millford and west of Mulroy Bay. — 

 Green, flaggy, with a peculiar purplish iron staining, or parting in 

 the joint planes. Small quarries were opened in several places to 

 procure stones principally for walling purposes. The stone dresses 

 well, but in one quarry the mineral in the joints disqualifies it ; as 

 even a small portion of one of these partings will stain the stone 

 and those in its vicinity. In a second quarry these iron partings do 

 not appear to be so prevalent, and good sized stones might be 

 raised. 



Rough Park, about two miles N.E. of Letterkenny. — Apparently 

 a bedded sheet of whinstone ; green ; flaggy ; compact ; dresses 

 easily. Has been quarried in two places, and used as building 

 stones, quoins, kerbs, and flagging, in Letterkenny. Durable as a 

 building- stone and as kerbs, but not so good in flagging. 



Lissnanan, about a mile N.N.E. of Letterkenny. — A very 

 similar stone to that of Roughpark ; lately used in Letterkenny for 

 kerbs. 



In the county between Lissnanan and Roughpark there are ex- 

 posures of from two to four sheets of these green flaggy whinstones ; 

 but these are quarried only in the above townland. At the present 

 time cut and dressed stone required in Letterkenny is brought all the 

 way from near Strabane, Co. Tyrone ; but this expense might be 

 saved if a good and proper quarry was opened in one of these whin- 

 stone exposures. The vein in Hough Park is very favourably 

 situated, being in a rise of ground, and near a good public road ; 

 while the stone in it seems capable of being raised of sufficiently 

 large and long scantlings to suit the requirements of the town. 



