Geological magazine . y, Geology of Colonsay and Oronsay (Mem. Geol. Surv. GreatBritain, 1911). JF. B, Wright—Submerged Forests in Donegal Lakes. 117 be seen in the position of growth, but in three of the cases the outletof the lake is through a peat-bog, so that no conclusion regardingthe failure of the outflow during the growth of the trees could bebased on them. In the remaining four (Loughs Bannus, Avehy,Drumgun, and Afurnagh) the outlet is over rock or boulder-clar, butthe last-named is open to exception, as it is extensively marginedby peat, through which it may possibly at one time have
Geological magazine . y, Geology of Colonsay and Oronsay (Mem. Geol. Surv. GreatBritain, 1911). JF. B, Wright—Submerged Forests in Donegal Lakes. 117 be seen in the position of growth, but in three of the cases the outletof the lake is through a peat-bog, so that no conclusion regardingthe failure of the outflow during the growth of the trees could bebased on them. In the remaining four (Loughs Bannus, Avehy,Drumgun, and Afurnagh) the outlet is over rock or boulder-clar, butthe last-named is open to exception, as it is extensively marginedby peat, through which it may possibly at one time have had a lowerdrainage. Lough Bannus is situated on the Donegal Road, 2 miles ofPettigo. Its surroundings are shown in Fig. 1. It lies amongdrumlins, and has its outflow to the east over boulder-clay, the stream,however, soon entering a little rocky valley without any great outlet has been lowered by artificial cutting to the extent ofabout two feet, and tliere is an abandoned shore-line about the same. ? drumlini., Fig. 1. Map of Bannus Lough, showing the position of the submerged treestumps and the contours of the surrounding ground. height above the water surface round the south side of the lake. It isclear, therefore, that in its natural state the lake was some two feetor so higher than at piesent. Tree stumps, submerged even at thepresent day, have been observed in two places, one on the northernshore and one on the eastern. The latter appear to be in the positionof growth, the former are more doubtfully so. Lough Avehy (Fig. 2) is on the Ballintra Road, 4| miles westof Pettigo. Its southern and western shores are formed of boulder-clay, and its northern and eastern of crystalline schists. It hascut fairly steep scarps, five or ten feet high, in the boulder-clayon the south side ; but these are no longer being eroded, for thelevel of the lake has been lowered from two to three feet, apparentlyby artificial drainage, and there is an abandoned shore-line at a
Size: 1679px × 1488px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1860, booksubjectgeology, bookyear1864
