O'Eeilly — On Jointing in Rocks about Dublin Bay, 8fc. 303 



Ho'wtli — continued. 



231 . Soutli side, east of batting-place, at point called the 



" "Worn-hole," vertical quartz veins, 

 very distinct with parallel ones, . 



232. ,, opposite dwelling-house, joint dipping east, 



233. • ,, about 350 to 400 yards east of bathing- 



place, great vertical joint, 3 feet broad 

 in an apparently altered rock, greatly 

 weathered, ...... 



■234. Drumleck Point, east of great fissiire in greenstone 



rock, ....... 



235. ,, cross jointing, . . . . . 



236. ,, Bay, west side of, vertical joint, 



237. ,, "Broad Strand," immense face of jointing 



on east side of bay, extending from top 

 to bottom of cliff, .... 



238. ,, "Lion's Head," little promontory near 



the Bailey Light, .... 



Ireland's Eye : — 



239. Fault in slate rock, towards south-east point, 



240. At south-east point, in black mica slates (Thulla 



Eocks), 



241. On south-east side, just south of fii'st creek, in slate 



rocks, jointing in, ..... . 



242. The west side of first creek and east side of the 



detached rock called " The Stag," 



243. North of Rowan's Rocks, in little creek on east side, 



cross jointing at the entrance, .... 



244. Jointing running across the mouth of same, nearly 



vertical, ........ 



245. East side, apparent contact of quartzite with dark 



shales (Samphire Hole), ..... 



246. In Samphire Hole, 



247. In cave, 



248. North-east point, well-marked vertical jointing in 



quartzite under " Stags," 



249. ,, vertical joint frequent and well marked, 



apparently parallel to axis of gut between 

 "Stags," 



250. Middle of Island, to the north, jointing in boss of 



white quartzite, ..... 



251. 300 yards east of Martello Tower, well-marked 



vertical joint, mth slight dip to west in 

 quartzite, 



252. ,, ,, well-marked cross jointing, 



running towards Tower, 



253. ,, well-marked jointing, running towards 



Skerries, ...... 



254. Apparent contact face of quartzites with altered 



shales, 100 yards north of St. JSTessan's 

 Church, ...... 



Howth : — 



255. Centre of Hill, jointing in slate rock, much broken 



and weathered, ..... 

 256. 

 257. ,, trench opened on jointing, 



Nm. 



23^-24° E. 

 7°-8' W. 



33°-34'' "W. 



5'W. 

 67°-68° W. 

 47°-48° W. 



3°-5° W. 

 39° E. 



87°-88° E. 

 13^-14° E. 

 43°-44° W. 

 36°-37° E. 

 730-740 w. 



3°-5 W. 



68°-70° W. 

 50°- 60° W. 

 50°-56° W. 



75°-76° W. 



3°-5° W. 

 84°-85° W. 



53° E. 

 32°-33° W. 

 26°-27° W. 



77° W. 



71° E. 



69° E. 



38°-40° E. 



