1912-13 ] 



649 



2nd. — A period of accumulation of glacial materials — snow, 

 neve, ice — along the axis originally suggested by Mr. 

 Maxwell Close, and at first adopted by Prof. Hull as the 

 oldest known in Ireland. 

 3rd. — Local accumulations in mountain groups. 

 To these I have recently found it necessary to add another 

 important ice-flow, intermediate between the first and second 

 moving southwards over parts of Ulster, of which evidence is found 

 at least 12 miles inland, as previously mentioned. We may now 

 proceed to consider the phenomena resulting from these systems 

 of glaciation, beginning with the first. 



EARLIEST BOULDER-CLAY. 



Evidence for the incoming of thick ice from the Irish Sea, 

 up over the eastern escarpment of the Antrim plateau, has already 

 been referred to. Further evidence is available at Knockan Hill, 

 near Broughshane, where fragments of Chalk, lithomarge, and 

 pavement are contained in beds of sand and gravel, and must 

 have come from the eastward. I do not dwell upon this here, as 

 the subject is dealt with in the recently issued Survey Memoir.* 

 Reverting to the region now especially in view, one of the most 

 striking facts met with is the occurrence of hard compact brown 

 Boulder-Clay derived almost wholly from basalt, but containing 

 some chalk and flint fragments, with smooth and scratched 

 pebbles and stones of basalt, in a stream bounding Ardinarrive, 

 two miles west of the Roe and six miles west of the nearest 

 possible, as well as the most likely source, of the clay and 

 enclosed fragments, f So far as I have seen, this is the only 

 instance of such a clay in the Roe Valley ; indeed, in view of the 

 subsequent ice movements presently to be dealt with, much 

 evidence of the kind could scarcely be expected to survive. 

 Closely corresponding evidence, however, is to be observed in a 

 stream-bank at Bollee, on the east side of the valley, where layers 

 of fine silt, gravel, and large rounded blocks — all derived from 



*" The Interbasaltic Rocks of North-east Ireland," p. 71. 

 f See Note B at end of Paper. 



