90 J. S. G-AEDNEE OX THE LOWEE EOCEI<rE PLAITT-BEDS 



lio more rods to go deeper." A boring at Sandy Bay gave, according 



to Giiffiths * :— 



ft. in. 



Blue clay 10 



Black limite mixed with blue clay 25 



Clav 2 6 



BlackHguite 20 



Clay 4 



Black Lignite 15 



76 6 



The area on the Lough over which silicified wood is found extends 

 from Lungannon to Gleiiaxj, a distance of 20 miles. Mr. Gray, of 

 Belfast, has found petrified wood from the drift at Coleraine, taken 

 from a well in the Boulder-clay, 40 miles northward from the 

 mouth of the Crumlin river. Also from the Boulder-clay in a deep 

 cutting at the back of the site for a manse at Cullybackey, 20 miles, 

 and from a cutting in the Boulder-clay for a road between Eandalstone 

 and Toome, 10 miles north of the mouth of the Crumlin. On the 

 south side Mr. Gray has only observed it in the drift-gravels within 

 the Maze race-course, 12 miles E. by S. from the same point, 



Lawrencetown t, where siliceous lignite has been found in trap, 

 is 17 miles south of the above point. Mr. Gray also calls attention 

 to the fact that lignite like that of Lough Keagh crops out at 

 Dundrod, half way between Crumlin and Belfasr i. These are 

 outliers, and interesting as showing the extent of the deposit before 

 it was denuded. It is hardly possible for the silicified wood to have 

 travelled north during the Glacial Epoch unless the physical features 

 of the country were completely reversed ; and I believe it is a weU- 

 established fact that the materials in the Boulder-clay are derived 

 from the north ; and, if such be actually the case, there is no escape 

 from the conclusion that the Lough-x^eagh beds, or beds similar to 

 them, once had a greater extension by at least 4:0 miles in a 

 northerly direction and have since been entirely swept away. The 

 view of their former greater extension is further supported by the 

 fact that at Dernagh, parish of Clonor, not far from the houndary 

 of the dejwsit, the beds were not penetrated through by a bore 173 

 feet deep §. 



* Portlock's Eeport, p. 167. 



t In the Proc. Belfast Naturalists' Field Club, 10th Annual Eeport, 1873, 

 p. 39, Mr. G-ray described "the occurrence of sificified vrood in the basalt at 

 Lawrencetown, where there is a bed of lignite in the basalt about 30 feet below 

 the surface, and in this lignite there are layers of wood charged with siliceous 

 matter, and resembling the wood erroneously supposed to be petrified by the 

 waters of Lough Xeagh. The latter is often foimd quite hard outside ; but 

 when broken, portions of the inside are quite soft and fibrous, like lignite, and 

 pass from soft wood into compact stone, the semisiUceous portions being 

 almost identical with the hard portions of the Lawerencetown lignite." This 

 fact seemed to the author to supply the connecting link between the silicified 

 woods and the basalts described by Portlock. 



I The above facts, communicated to me by Mr. Gray, have not previously 

 been published in this definite form. 



§ Hardman, Joum. Eoy. Geol. Soe. teland, vol iv. p. 176. 



