1869.] NICOL PARALLEL EOADS. 285 



former existence of a narrow sea-strait. Here, then, it appears to 

 me we have undoubted proof that the lines have been formed by the 

 sea, and not by lakes. 



A few observations taken from notes made on the spot may render 

 this statement plainer. The highest line is that in Glen Gloy. The 

 valley by which the lake is assumed to have drained into Glen Eoy 

 is very narrow and encumbered with detritus from the hills on the 

 sides. The summit-level is flat and marshy, and it appeared to me 

 considerably below the level of the line. On the other hand, a line 

 of stones, as if washed out of the detritus, appeared to show that the 

 sea or loch had extended quite through the strait. I observed no 

 indication of any stream of water larger than the present small 

 rivulet having ever run here. But as the difference in height of 

 this line from the upper line in Glen Eoy is not great, and the 

 erosive action of the river might thus have been limited, I shall not 

 mention any other details. 



The next pass is that from Glen Eoy to the Spey. If a lake ever 

 filled the valley of the Eoy to the level of the upper line, a great 

 river, fully equal to the Eoy where it now joins the Spean, must 

 have flowed through this pass. In time of floods, when swollen by 

 the western rains and melting snows and glacier-ice, it ought to 

 have left no uncertain mark of its passage over the watershed and 

 down the vaUey of the Spey ; but I looked in vain for any indica- 

 tion of the former presence of such a mighty stream. It has cut 

 no notch in the ridge or on the sloping declivity to Loch Spey ; it 

 has formed no delta in this lonely tarn. The broad flat strath of 

 the Spey shows only the narrow channel through which the present 

 streamlet winds its way to the sea. ISTo one who has ever studied 

 the effects of running water in such situations could doubt that even 

 in a few days or weeks such a river as the present Eoy (and the old 

 river at least could not have been smaller) would leave a groove in 

 the soft alluvial hollow which centuries would fail to obliterate. 

 The rapid running stream must have cut a deeper line on the low 

 haugh than the mere wave-wash of a shut-in mountain-lake on the 

 slope of the hill. Yet the one is distinctly visible for miles round 

 and round; of the other there is not the faintest trace. It is a 

 physical impossibility that the lake should have left such a deep 

 and distinct line, and that the river should have flowed through the 

 gorge and down the valley for the same time without leaving any 

 mark of its presence. 



On the other hand there are clear indications of the pass having 

 once been a sea-strait. The bottom is broad and flat ; a notch is 

 cut horizontally along the side of the hill where the water once 

 stood, and a distinct line of stones left where the water has washed 

 away the detritus. In other words, there is an old wave- washed 

 beach. Then a curious series of little rounded bare knolls rise up 

 in the old channel. From a lateral corry below Loch Spey great 

 masses of detritus project into the main valley, but these are spread 

 out and levelled down ; as if thrown into the sea, not as if heaped 

 up in a river-valley. It is scarcely worth mentioning, though im- 



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