4°-5° 



W. 



72^-73° 



w. 



7°-8= 



E. 



6'-7° 



E. 



0'E.EiLLY — On Jointing in Hocks about Dublin, 8fc. 123 



Donabate Coast — eoniinued. 



Fault, -with caunting of strata, near Martello Tower, 



Direction of strata here, 



The beds here highly pitched (N"»- 60°— 70") and serrated 

 on the edges, by very frequent and close jointing, in 

 a remarkable manner, ...... 



)> )> )j )) J' !» )' n 



This character continues to show itself in the remarkable 

 successson of beds, which continue round N. to the 

 conglomerates, forming the entrance to Rush Harbour, 

 which evidently corresponds to a line of jointing, . 7o''-76° W. 



On the north side of the harbour the Umestone lies flat, 



or at low angles, and presents sparry jointing at . 53°-54:° E. 



[At the northern extremity of Eush Strand, the strata 

 nearly vertical, with chert cores (Dip to N. at 80°). 

 Direction N-"- 80° E.] 



Fault cutting the shales here with slickenside, . . 23°-24° W. 



,, ,, ,, chert beds, 26°-26° E. 



Fault crossing these, 75°-76° E. 



A spary joint crossing these, ..... 27°-28° W. 



A set of highly-contorted beds here undergoing marked de- 

 composition, apparently from oxydation of iron pyrites ; 

 evidently in some way connected with the stream which 

 comes in here, and which presents two directions, one 28°-30° "W. 

 And another, giving rise to a well-marked ravine, . 73°-7i° W. 



Direction of beds under Giant's Hill, N"^- 88°-90° E. 

 Two or three sparry joints crossing these at the north- 

 east extremity of little bay or inlet, .... 25°-26° W. 

 Thick jointing, repeated, crossing north-east end of bay, 



in direction of Rush point, ..... 2°-3° E. 



Direction of beds here (quite vertical), .... 75°-76° "W. 

 Here Brook's Inlet intervenes with synclinal trough, 

 on the north side of inlet beds dip to south at 

 40°-45°. 

 Heavy joiating traversing Drumanagh promontory, . 6°-7° E. 



On the western shore of the Inlet (Eoaring "Well 

 Inlet) the chert beds are decomposed as at north end 

 of Eush Strand, with strong indications of manga- 

 nese and purple ochre. 



Mass of Dolomite on south-east side of Drumanagh pro- 

 montory, looking towards Lambay Island, . . 26°-27° W. 



The beds south of the Martello Tower, dipping south at 



35°-40°. Jointing in these beds, .... 34°-35° W. 



Great fault under Martello Tower, 3 ft. thick in places, 

 being a conglomerate of limestone boulders, cemented 

 bycalcspar, ........ 33°-34° "W. 



Parallel companion joints close to this, some of them 



strongly marked, „ ,, 



Crossed by vertical jointing, 55°-56° E. 



Repeated jointing on north side of fault, . . . 32°-33° W". 



. I. A. PEOC, SE-R. II. VOL. IV. — SCIENCE. S 



