OO J. S. eAEDNER ON THE LOWEE EOCENE PLANT-BEDS 



basalts are in the Ballinderry river (where it is described by Portlock 



as " alternate layers of sand ard imperfect lignite, in fragments 1 to 



4 inches thick," 6 feet ; bine clay, no depth stated ; basalt) and in 



the Crumlin river* (where it is only 7 feet thick, 3 of which are 



coarse gravelly matter and 1 foot a bed with shells). Mr. Swanston f 



and others have shown that in this latter example a drift with 



fresh-looking shells of Mytilus eclulis t liad been mistaken for the 



Lough-]S!'eagh beds ; while even at Ballinderry the section does not 



seem to have been accurately observed, and might be in a redeposited 



mass. There is great probability, however, that a large part of the 



formation may actually rest upon basalt ; but the view embraced by 



the Geological Survey of Ireland and others, that the entire formation 



is newer than the latest basalts, seems opposed to the evidence ; and 



the inferences that it is Pliocene, Pleistocene, and even practically 



the delta-formation of existing rivers, and intimately connected with 



the present lake, are, to my mind, wholly unwarranted. It may be, 



as at Bovey, that the beds are in places, however, covered with a recent 



head. The position and inclination of the beds would lead me to 



place them low down among the basalts, and in the Glenav}' river a 



mass of basalt all but rests upon them. This relative position has 



been explained by supposing that the basalt forms an old cliff-line 



against which the lacustrine beds terminate ; but Mr. Swanston has 



combated these views, and believes the Lough-Neagh Beds to be 



inter-basaltic. I think the further considerations to be brought 



forward support his belief. 



A question no less vexed, and inseparable from the other, is the 

 age of the celebrated petrified wood of Lough i^eagh." The best 

 recorded fact concerning it is the oft-quoted statement of Barton §, 

 a resident and very careful observer, that there was a bank some 12 

 feet high and 90 feet from the lake, at a place called Aahaness, 

 opposite Eam's Island, where a section was obtained by digging, 

 in 1757, as follows : — " The upper stratum was a bed of red clay, 3 

 feet deep ; the second blue clay, 4 feet ; the third black wood, 4 

 feet, reposing on another stratum of clay. This stratum of wood 

 is of one uniform mass, and is capable of being cut with a spade. 

 Sometimes the wood will not easily break ; in that case it requires the 

 aid of some other tool to separate it from the mass ; and may, if 

 properly done, afford a block of 200, 300, or 400 lbs., which, being 

 carefully examined, is found to consist more or less of stone "|| . This 

 statement is very explicit and is corroborated by Dr. Scouler, 

 Professor of Mineralogy to the Boyal Dublin Society, who adds : — 



* Hardman, Geol. Mag. 1876, p. 556. 



t Swanston, ibid. 1879, p. 64. 



X Mr. Swanston adds in a letter to me that the presence of Foraminifera 

 with the Mytilus proves these clays to have been of marine origin, and the pre- 

 sence of glaciated pebbles in the " 3 feet of coarse gravelly matter " puts them 

 into the drift. 



§ Eichard Barton, B.D., ' Lectures on L. Neagh,' 1751, pp. 5 & 139, also 

 discussed at length in Portlock's Eeport, p. 75. 



II Eev. J. Dubourdieu, 'Statistical Survey of the County of Antrim,' 1812, 

 p. 187, states that the wood is often only partly stone, the brittle wood joining 

 on in one continuous piece. 



