154 Archdeacon Verschoyle on the Geology of the North Coast of 



sand-banks of Bartra Island and Scurmore^ to the north of whichj on the Sligo 

 shore, is a continuation of the trachyte, first seen in Ross. From this point to 

 BalHsadere Bay, the coast is composed of mountain limestone and the asso- 

 ciated beds of sandstone. These strata are strikingly displayed in the preci- 

 pitous sides of Knock-na-ree, to the east of BalHsadere Bay, and are streaked 

 horizontally with beds of light grey rock, tinged with various shades of purple 

 and yellow ; and are skirted by a talus of fragments from the cliff above. 



1 have thought it convenient thus to separate the general sketch of the 

 district, from those geological details, which are the more immediate object 

 of this communication. 



Second Section. 



In considering the subject of this section, I adopt the arrangement of the 

 Rev. William Conybeare, in his Outlines of the Geology of England. Com- 

 mencing, therefore, with the highest formation in the district, the following 

 series will be described : 



Intermediate order , 



The inferior or primary rocks 



'A. Carboniferous limestone. 



B. Ditto oolitic. 



C. Calcareous and argillaceous shale and grit underlying the 

 limestone. 



-D. Old red sandstone and conglomerate. 



E. Quartz rock. 



F. Gneiss. 



G. Mica slate and hornblende slate. 

 Ih. Granite. 



I. Trap rocks, porphyry, and basalt. 

 K. Trachyte. 



Intermediate Order. 

 A. Carboniferous Limestone. 

 This formation prevails on the north and south of the Ox Mountains. Ben- 

 bulben (1697 feet) and Knock na Ree (1057) on the north of the chain; and 

 Knock na Shee (480) on the south, are entirely formed of it. The lower beds 

 contain nodules of black chert, and invest the organic remains which abound 

 in limestone throughout Ireland. It varies in texture from compact to highly 

 crystalline, and in colour from grey to light brown ; its specific gravity 

 ranging from 2"670 to 2-685. Arragonite, fluor, brown spar, pyrites, and 

 quartz crystals are often imbedded in it, or line rifts and fissures. A vein of 

 sulphuret of lead accompanied by blende and iron pyrites, has been worked 

 at BalHsadere, but is now abandoned. It is said to have been very rich in 



