2I2 [Proc. B.N.F.C., 



alternated and capped by thick beds of saliferous clays, constitut- 

 ing what are known as the Triassic system, and attaining in 

 our district a thickness of probably 2,000 feet. Our triassic rocks 

 yield a limited supply of gypsum, in addition to sandstone, for 

 building purposes. The saliferous marls of the triassic system are 

 the source of an active industry in the production of salt, of which 

 we have a rich supply around Carrickfergus. The triassic system 

 is sometimes called the new red sandstone in contradistinction to 

 the old red sandstone, the one being newer than the coal or 

 carboniferous, and the other being older than the coal. After the 

 lagoons or salt lakes of the triassic epoch, the marine condition 

 of the lias, and the dry land of the Oolite epoch, we are next 

 introduced to the profound deposits of the cretaceous sea, where 

 our chalk or white limestone was deposited during the lapse 

 of many thousand years. Since the outbursts of igneous action 

 that elevated the granites of Mourne after the carboniferous age 

 no igneous forces were manifested to the same extent in our 

 district until the trappean outburst in the tertiary period, when 

 the long-exposed surface of the chalk formation was covered by a 

 succession of basaltic overflows, now constituting the trappean 

 plateau of Antrim, including the world-famed Giant's Causeway 

 geological phenomena. The basaltic material of which the 

 Antrim plateau is composed was not ejected in a few violent 

 outbursts, but accumulated slowly by a series of overlapping flows 

 from fissure vents widely distributed over the area in action, the 

 iron clay bands that are to be seen between the flows indicating 

 periods of rest, during which the surface of the basalt was exposed 

 to atmospheric denudation for periods of various lengths. The 

 great iron ore band between the upper and the lower basalts 

 of Antrim indicates a prolonged period of rest, during which 

 rivers and lakes were formed, forests grew, and a rich vegetation 

 clothed the landscape. All this was completely overturned by 

 the subsequent outburst of volcanic energy that produced the 

 upper basalts, converting the vegetation into lignite coal, the lake 



