Irish Volcanoes. 177 



All the phenomena of the district are best seen on and near 

 the coast ; and the two or three honrs taken up by the railway 

 transit, are not more than a fit introduction to them. From 

 the very nature of the case the rock poured out from the 

 volcanoes is flat, and covers all varieties of surfaces pretty 

 equally. Here and there there are gaps, and occasionally hills 

 of sand, clay, and large or small boulders, cover the flat sur- 

 face, preventing monotony. 



The interesting points of the district are three — the great 

 lake, the Causeway, and the coast road to Lame from the 

 Causeway, passing F airhead. 



Lough Neagh is a singular rectangular piece of water, 

 nearly sixty miles in circumference. The ordinary level of its 

 surface is about forty feet above the sea, and much of the lake 

 is of very moderate depth • so that if there were free commu- 

 nication with the ocean, it would soon be greatly reduced. It 

 receives the waters of eight small streams, while only a single 

 river runs out from it towards the north, reaching the sea at 

 Coleraine. This river, the Lower Bann, passes through a 

 second but much smaller pool (Lough Beg) immediately after 

 leaving Lough Neagh, and in it there is a natural obstruction 

 that prevents the drainage of the lake. By clearing away the 

 rocks in the course of the Lower Bann, the stream has been 

 quickened and the lake lowered, but a band of basaltic rock in 

 Lough Beg effectually prevents any further reduction. 



More than a century ago, a certain Mr. Richard Barton 

 published a series of lectures on the subject of this lake. At 

 that time, also (1751), several memoirs were written concerning 

 it for the benefit of the Royal Society, and several maps of the 

 lake were published. From these it would seem that there were 

 once many more islands than now exist, from which it is pro- 

 bable that a large decrease of depth has taken place, those 

 islands which were near the shore being now parts of the main 

 land, and the area of the lake diminished. 



The peculiar natural productions of Lough Neagh in the 

 mineral kingdom are fossil wood and a number of so-called 

 gemi. These are not quite undeserving of the name, and the 

 celebrated Boyle, in his treatise on gems, remarks, " there is a 

 lake in the north of Ireland which supports fish as well as 

 other lakes, where, nevertheless, in the bottom of it are rocks 

 to which adhere masses of beautiful figured substances, in 

 clearness and transparencj^ imitating crystal." Innumerable 

 specimens of chalcedony, agate, jasper, and common opal are 

 found among the pebbles of the shores of the lake. The frag- 

 ments of fossil wood are very numerous, and are sometimes so 

 large as to weigh one or two hundredweight ; the largest 

 specimen recorded seems, indeed, to have weighed about seven 



