10 



the ground having been smoothed down, and the inequalities 

 caused by the dislocation of the beds having been worn away, 

 by denuding agencies before the clays were deposited. It was 

 to the depression of the surface through the agency of these 

 faults that, according to Mr. Hardman, the formation of the lake 

 is due. This lake, therefore, forms an illustration of a basin 

 formed by the mechanical action of faults in the strata, assisted 

 by the action of running water." 



Lakes of glacial origin are found in many parts of Ireland, but 

 chiefly among mountain glens and in front of valleys. These 

 lake-basins are hollow, scooped out of the rock by the action of 

 ice passing over its surface, or else, as Dr. Hull has pointed out, 

 " where moraine matter or boulder clay has been heaped up across 

 a valley or hollow so as to form an embankment for the streams 

 which enter the depression from above." The class of lakes which 

 are due to chemical solution are chiefly found in the great central 

 plain of Ireland, but they are met with in all limestone districts. 

 They are, " strictly speaking, irregular hollows dissolved out of 

 the limestone floor and filled with water." Dr. Hull says that 

 in examining the form of these lakes of chemical solution, 

 " from the manner in which they widen out in some places, and 

 in others become contracted, it will generally be found that they 

 spread themselves out over the ground formed of limestone, 

 and contract where non-calcareous rocks form the bed and 

 margin of the lake. Lough Derg is an illustration of this." 



Mr. Patterson then directed attention to the mention made 

 in the " Four Masters " concerning the eruption of lakes, the 

 first eruption being in the year of the world 2532. The passage, 

 as translated by O'Donovan, reads — " The age of the world 

 2532. The eruption of Loch Con and Loch Techet in this 

 year." O'Donovan explains that Loch Con is a large lake in 

 the barony of Tirauley, and County of Mayo. In the age of 

 the world 3506 the eruption of a large number of the Irish lakes 

 took place. Amongst these was Loch Laogh, the ancient name 

 of Belfast Lough, and which means in Irish the Lake of the 

 Calf. The early monkish writers translated the name into 



