Clakk — Evidence of Displacement of Car'loniferous Strata, Co. Sligo. 227 



It is easy to find where the dykes in the Donaghintraine sandstones should 

 appear on the Aughris shore if they run straight across to sea. A careful 

 search in this region will reveal the three dykes again — or rather two of the 

 actual dykes, and unmistakable evidence of the third. Of one dyke there is 

 nothing left ; but there is a deep channel in the rocks, the sides of which show 

 the unmistakable ''platy structure" in the limestone which usually accompanies 

 a dyke, due to slight metaraorphism. The other two are visible, and are marked 

 by the Geological Sui-vey. They are, of course, the three dykes seen in the 

 sandstone. 



The point at which the Pollbrean dykes should reach the Aughris shore was 

 ascertained, but a most exhaustive search along the entire west coast of Aughris 

 revealed not a trace of any dyke, except those just described, to the south. 



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DOTVO,!] h 



ClH-IltltfjO.tT.cK. 



I 



1) OTvag K.i.n. t ra.1. n.e- - 



SHALE, 



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SMLCS. 



Fig. 2. 



On the east coast of Aughris there is a narrow, deep inlet at Pollachurry. 

 It is similar to that at Oughmore, but does not now contain water, and is over- 

 grown with grass. The floor of this channel consists of a dyke of amygdaloidal 

 dolerite. This dyke is in a perfect straight line with the central dyke at 

 Pollbrean and Oughmore. The other dykes are also present ; the northern dyke 

 has diverged a short distance from the central, and the southern dyke has come 

 closer. None of them are marked on any of the maps, or mentioned in the 

 memoirs of the Geological Survey. 



It is obvious that in every case the dykes are the same three ; but where the 

 Pollbrean dykes should have reached Aiighris there is no trace of them. They 

 have been displaced from their course between the east and west shores of 

 Aughris, as weU as in the sandstone beneath the sea shown above. 



The first explanation of these facts which suggested itself was that these 

 dykes, running in a definite direction, were suddenly deflected from their course 



