1912-13.] 643 



absolutely none to be found in that direction. Instead of this a 

 boring made 2 miles from the south-west shore revealed 264 feet 

 in depth of the Lough clays under 30 feet of Boulder-Clay; and 

 Hardman, who records the facts, gives it as his own opinion that 

 the clay-beds have an aggregate of 500 feet in thickness. 



And, again, we must ask what becomes of the 700 feet of 

 so-called Lower Basalt at Divis, which could scarcely have failed 

 to spread — possibly in still greater thickness* — westward as far 

 as, indeed beyond, the lake. This also eludes us. The corres- 

 ponding disparity between the thickness at Divis, and the very 

 thin representation of true Lower Basalt at Templepatrick, has 

 already been pointed out. 



Again lignite, associated with "red pisolitic earth," is known 

 to occur between the Chalk and Basalt at Knocknadona, north- 

 west of Lisburn ; and can it safely be asserted that this is not a 

 representative of the lignite series of Lough Neagh, towards which 

 the ground maintains a gentle slope due to the general depression 

 of the lake-area ? The depression which initiated the formation 

 of the lake is of quite a mild degree as compared to the depth of 

 clay reported near the south-west border; and, while it is 

 comparatively easy to fancy how alluvial and delta deposits might 

 soon fill up so great a depth, one factor in the problem should 

 not be overlooked : it is this, that the present Blackwater and 

 Bann could not have eroded, and disposed of the products of erosion 

 of so great a hollow — i.e., about 250 feet for certain, and 450 feet 

 probable. The Bann at present flows over shallows of basalt at 

 Portglenone; and the Lagan, a possible alternate course for the 

 drainage, also flows upon rock near Lisburn. 



*For it will be shown that in pre-volcanic times a valley existed — that of 

 the old Blackwater — with its gentle descents from east and west, which would 

 have facilitated the accumulation of Lower Basalt therr, if such a thickness of 

 lavas as 700 feet were heaped up on its east side, only a few miles off. At the 

 stage of Upper TSasalt outpourings, there may have been so great a thickness, 

 even greater, but this, like as at so many other points in Antrim, has been 

 carried off by denudation. The softer beds beneath were preserved by bein'* 

 at a lower level than that at which waste was proceeding. 



