554 Scientific Proceedings, Royal Dublin Society. 



DOWN. 



Rocks of Ordovician age occupy the major portion of this 

 county ; but in these to the southward, among the Mourne Moun- 

 tains, in the vicinity of Carlingford Lough, are intrudes of 

 granite and other Exotic rocks. Two very small tracts of Car- 

 boniferous rocks occur, one on the margin of Carlingford Lough, 

 and the other in the vicinity of Castle-espie, at the north end of 

 Strangford Lough ; while to the north-west and north, in the 

 valley of the Lagan, northward of Comber, and in the neighbour- 

 hood of Newtownards, are Triassic. In the valley of the Lagan, 

 over the Trias, are other Mesozoic rocks, and the Eocene (?) 

 dolerytes, with their accompanying basal beds. 



Ordovician. — The various grits that occur in places in the 

 rocks of this group seem to be only used for local purposes, as in 

 the area there is no quarry of note. In the district the slate rocks 

 are usually used for rubble work ; and granite, or Trias sandstone, 

 for groins, dressings, and other cut-stone purposes. At Ballygowan 

 there is a stone used in the National School, which Mr. Grey 

 reports as "very hard, durable, and dark-coloured — nearly black." 



Near the " Stone Circle," Millan Bay, and to the south-west of 

 Slievenagriddle, flags of large size can be obtained. 



Triassic. — In the quarries along the valley of the Lagan the 

 stone, nearly invariably, is of a deep-red, or brick-colour, and more 

 or less soft and argillaceous. It has been largely used for local 

 purposes, especially for the bridges of the Ulster (now the Grreat 

 Northern) Railway. There is a considerable quarry at Kilvarlin, 

 near Moira. 



To the north of the county, at Scrabo Hill, near Newtownards, 

 there is a better class of stone. Here there are different quarries, 

 in which the stone varies greatly in colour and quality, there being 

 shades of grey, yellow, and red; some are argillaceous, others 

 silicious, while they may be friable, or have concealed joints or 

 vests ; therefore they have to be selected with great care if good 

 and uniform work is required. 



[Blasting is too prevalent in this quarry. Good stones, with a little extra trouble, 

 might be raised by the crowbar and wedge, while, if raised with powder, they are 



