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limestone is over the level of the sea, at its upper surface, 300 feet ; at 

 Bengore Head it is probably under it, at about 150 to 200 feet, making 

 here a difference of between 400 and 500 feet in the surface of the 

 chalk. At Port Braddon, where the two rocks join vertically, is pro- 

 bably the seat of this dislocation. I must defer the explanation of this 

 to a future opportunity. 



The chalk in Knocklayd Mountain stands at 87 0 feet high ; at Bal- 

 leny, one mile north of Armoy, it stands at 270 feet, making a dif- 

 ference of 600 feet in height : they are about a mile asunder. The 

 band is nearly level at both places, showing that there must be a fault 

 between them, which runs from Ballycastle by the western base of 

 Knocklayd, and so on southwards. I shall further describe this fault 

 hereafter. 



Again, at Slieve Gallion, in Derry, the chalk stands at 1500 feet 

 above sea level, while between Magherafelt and Coagh it varies from 

 170 to 312, or it is 250 feet average, making a difference of 1250 feet 

 between the band near the top of Slieve Gallion and the equivalent of 

 the same band in the low plateau at the eastern base of that mountain, 

 between it and Lough Neagh. The fault in this case must be at the 

 eastern base of Slieve Gallion, which is about three miles east from the 

 patch of chalk near its summit. 



In the cases of Knocklayd and Slieve Gallion there are some sugges- 

 tions of a speculative character connected with them, worthy of a few 

 observations. 



When we find chalk in the middle of Knocklayd 870 feet high, 

 and similar chalk on the north shore at the level of the ocean, the beds 

 of both lying level, whether should we say the Knocklayd chalk has 

 been elevated from its original position, or the chalk of the shore de- 

 pressed ? Either case would produce a disruption of the chalk, a dif- 

 ference of level, and the same effect. 



There are 1540 square miles of trap in Antrim and Deny, all in 

 connexion, with chalk under it. It stretches from Ballintoy to Stew- 

 artstown, in a straight line, at nearly the same level, a distance of fifty 

 miles. The Knocklayd platform of mica slate is 110 square miles. 

 Standing still, or being elevated, whatever movement affected it pro- 

 bably affected it as a unit, all at one time together. It appears more 

 rational to suppose that the small area — 110 square miles — was ele- 

 vated, than that the large one — 1540 square miles — was depressed. 

 We talk every day of the elevation of mountains, and say the Alps 

 were elevated, or the Mourne Mountains. I believe the trap, at the 

 usual general low level, was still ; and that the Knocklayd platform of 

 mica slate was put in motion, and was elevated in one mass together, 

 parts of it undergoing slight modifications of level afterwards, from 

 cracking and settling down. 



Again, on Slieve Gallion, in Derry, the patch of chalk, covered with 

 trap, similar to that at Knocklayd, stands at 1500 feet above sea level; 

 the low ground between Coagh and Magherafelt, composed of similar 

 formation, forming a plateau between Slieve Gallion and Lough Neagb, 



