Kinahan — Formation of Lough Corrih. 493 



likely that it was ever joined to " The Old Lough " as a rock island 

 and a shallow channel with a rocky bottom intervene. 



If this gut could not have been excavated by subaerial agencies, 

 was it formed by ice ? and was ice the principal agent that denuded 

 out the " Kock-basin " of Lough Corrib ? 



It has before been mentioned that the rocks are dressed and 

 striated under the water of low summer level ; this of itself is a 

 fact in favour of ice action. Of the striee there are various systems, 

 the oldest bearing about N.W. and S.E, ; a newer running with the 

 lie of the Eock-basin of Lough Corrib, and the newest following- 

 different lines according to the direction of the transverse valleys 

 that open into Lough Corrib. These may respectively be called the 

 primary stri^, the secondary stri^ of Lough Corrib, and the secondary 

 stride of the transverse valleys.^ The primary stri^ are very general 

 on the Carboniferous Limestone ground ; the secondary striae of 

 Lough Corrib have various bearings according to the turnings of the 

 valley, and coming down into them are the secondary striee of the 

 transverse valleys. From this it will be seen that three sets of 

 strige may occur in the valley of Lough Corrib. This is well marked 

 east of Oughterard, for thereabouts are found — the primary strige 

 bearing N. 40 E. ; the secondary strias of Lough Corrib bearing 

 N. SOW. ; and those of the Owenfough valley bearing N. 80 E. 



If ice can scoop out rock, " The Old Lough " may have been 

 principally formed at the same time as the primary striae (as the 

 general bearing (about N.E. and S.W.) of both is the same), by the 

 sheet or nappes of ice that is supposed at one time to have covered 

 Ireland. If the movement of this sheet of ice was from the N.E. it 

 would have pkmged over the high ground at • Cong and scooped out 

 a hole, having a much greater power if, previous to the ice period, a 

 lake, as before suggested, existed hereabouts. On looking at the 

 map (PI. XVIII.) it will be seen that "the deep" forks on either side 

 of Inchagoil, and that there are three small spaces in "The Old 

 Lough" which are less than 50 feet deep. These would seem to 

 be in favour of hills and hollows existing here previous to the 

 action of the ice. 



The previously mentioned deep gut on the north of Cam Seefin 

 would lie in the course of the glacier that came down the Maum 

 valley. At the west end of this gut there is a barrier of rocks across 

 the valley. If this barrier once extended farther east than it now 

 does, and if ice has a similar or greater power of cutting back a 



that in one place there is a hole exactly the same depth as the isolated hole in " The 

 Old Lo;!gh," viz., 152 feet; and also that in the metamorphic rocks there are beds 

 of limestone, one of which might possibly be so placed that it joined into the Carboni- 

 ferous Limestone, and through it the passage ran. However, against it is the fact 

 that in the neighbouring hills no subterranean passages occur, and the boundary 

 between the metamorphic rocks, and the Carboniferous Limestones can be traced by the 

 streams that ilow down the hills, taking the ground as soon as they come on the 

 latter. 



1 For particulars about primary and secondary striae, see Paper by the author 



"Notes on some of the Drift in Ireland "—read before the E.G.S.I. "Dublin 

 Quarterly Journal of Science," Oct., 1866. 



