35 



presence of foreign rocks in the clay and associated beds 

 2. The polishing and striation of boulders and blocks. 3. The 

 polishing and scratching of the parent rocks in situ. 4. The 

 darker and more dense clay being next the rock. 5. Partial 

 stratification near surface of clay hills. 6. Masses of sand, 

 roots of trees, &c, in the clay. 7. Eskers and sand and clay 

 beds with shells. 1. Erratic or perched rocks. In explana- 

 tion of this paper a large map of Ireland was exhibited 

 showing the contours of the country when submerged to depths 

 of 500 feet, 1,500 feet, and 2,000 feet, and also a diagram 

 illustrating the complete actions of land and sea ice upon a 

 coast line where there is a considerable rise of tide. 



Mr. Young next explained, by means of a large map of the 

 district adjoiningCarrickfergus,theline of a great fault or down 

 throw in the Trap, Chalk, and other beds below them extending 

 across the Commons, the higher level of the Chalk where it is 

 exposed being about 600 feet, and the lower escarpment being 

 about 400 feet above sea-level. He adduced reasons for con- 

 cluding that the gap in the steep rocky face of the Knockagh, 

 known as the Stony Glen, was on the western extremity of 

 this dislocation, thence it was traced to a point on the South 

 Woodburn, where a reservoir had been intended for the Belfast 

 water supply, but prudently abandoned. It is then found .on 

 the North Woodburn, at a short distance below the new 

 reservoir on that stream, and thence passes through the 

 open Commons to the curious cavern of Lignaca, near Lough 

 Mourne, from which cavern there is an underground channel 

 to the well-known Sulla Tober, where a considerable stream 

 bursts forth at the base of the lower Chalk escarpment. The 

 entire district southward of the line indicated has therefore 

 been depressed about 200 feet, and this occurred probably 

 during the last term of the glacial period. The eastern 

 boundary of this fault has not yet been clearly determined. 



