222 Proceedings of the Royal Irish. Academy. 



The bouldei^ were encountered in gi-eat numbers in the valley of the Finn 

 aljove Stranorlar. In a section, 12 feet high, in the Corlaeky Burn, 

 north-west of this place, only one small piece of granite was obtained, ^ while 

 careful search among countless boulders in the walls of Lettei-shambo to the 

 north of this occurrence failed to discover a siugle granite. A similar absence 

 of granite fragments and bouldei-s characterized the stream - section at 

 Ardnabroena on the southern slopes of Cark Mountain, though a few were 

 found in the better drift sections in the Srufiannaghallagh Eiyer, just below 

 this locality. At the head of the ovei-flow ehaunel, just north-west of 

 Cronaglaek, a single boulder of granite was observed, though in the fine 

 section near Stranabad Lower, some two miles south of this, none was detected. 

 A careful search in the magnificent section at Altadush, in the upper reaches 

 of the SwDly Yalley, was no better rewarded. 



One granite erratic was met with on the hUlside about one mile east of 

 New Mills, while a few were noted in the valley below the overflow channel, 

 south of Craignasaggart (672). In the fine sections^ exposed in the railway 

 cuttings at the junction south-east of Letterkenny, very few were observed ; 

 the limit of the dispersal is therefore not far from this town. This is 

 confirmed by the detection of a boulder near '' I'he Thorn," about two miles 

 E.-X.-E. of Letterkenny. 



Xo granites were encountered over the country between EUistria and 

 Kilmacrenan, nor were they met with in the scanty drift exposures in the 

 triangular area between this village, Letterkenny, and SwUly Bridge. This 

 region would therefore appear to lie outside the granite boulder country. Its 

 edge is near Tullyhall, where one or two small pieces were obtained. 



An occasional boulder was seen to the south-east of MOford and a few 

 along the eastern side of Mulroy Bay, e.g. at KerrykeeL They also occur 

 along the western shore of Lough SwUly and in the embayment to the north 

 of Knockalla, e.g. W. of Portsalon, becoming increasingly plentiful as traced 

 southwards towards Eathmeliou. 



These localities in the western region of dispersal, where boulders of 

 granite were and were not detected, together with numerous others which have 



' The section was composed of striated schist and quartzite, embedded in a matrix 

 derived from the disintegration of the former. In the small sections beneath the tnrf 

 round about trig. pt. 730 (on road), though schist and diorite with some quartzite were 

 obtained, no granite was observed. 



- The drift here consisted exclusively of schist, diorite, and quartzite. These rocks 

 plus granite formed the constituents of the drift exposed in the Srufiannaghallagh River. 



^ These are nearly all grassed over, but one, some 30 feet high, shows boulders and 

 fragments of schist and quartz. In addition to the occasional granite, quartzite, and 

 diorite. 



