EEMARKS ON GLEX EOT. 19 



from the curvature of the earth. A similar observation is also made 

 by Sir Thomas Dick Lauder/ I am confident that if Prof. Prestwich 

 had surveyed the lines upon the spot through a good spirit-level or 

 theodolite, instead of through the medium of the six-inch Ordnance 

 map at home, he would never have hazarded the statement which 

 he has made. The undeviating horizontality of the lines is in fact 

 one of the most interesting and remarkable features connected with 

 the phenomena, for it cannot be said that a progressive change of 

 level, or slope however slight, has been established in any direction 

 whatever. The altitude of the lines at their northern and southern 

 and likewise at their eastern and western extremities seems, accord- 

 ing to the Ordnance Survey, to be about the same ; and the height 

 halfway between corresponds also. 



In a former paper ^ I mentioned that I discovered a terrace at 

 the mouth of Loch Treig 30 feet higher than the Parallel Eoad in 

 the neighbourhood. The Ordnance Survey map on the six-inch 

 scale confirms this observation, and shows that the terrace extends 

 from the mouth of Corry Laire round to liOch Treig, sloping gradu- 

 ally upward near the loch to a height of 896 feet, or fully 40 feet 

 above the general level of the lowest Parallel Eoad, which is the 

 only one in that locality. It cannot therefore be due to the action 

 of the lake, but may have been a lateral terrace formed in some way 

 by the glaciers of Glen Treig and Corry Laire. The Ordnance map, 

 however, terms it a ' Parallel Eoad.' The real Parallel Eoad occurs 

 in the same neighbourhood at its usual height of about 855 feet, so 

 that this higher and sloping terrace is not owing to a superior 

 elevation of that ' road ' at this particular place : it is a distinct 

 mark due to some other cause. I point this out because Mr. James 

 Melvin in his paper ^ refers to it as a serious difficulty. 



X. Beach-pebbles aihb "Wave-actioi?^. 



Although it is commonly stated that there is an absence of 

 waterworn pebbles along the Parallel Eoads, yet these may be 

 found in some places where the lake was most exposed to agitation 

 by the wind. Eor example, near the top of Glen Eoy, the face of 

 the hill above Leek Eoy fronts a long opening down the glen, so 

 that it is exposed to the sweep of the south-westerly gales, and in 

 fact the wind blew with great force when I was upon it. Accord- 

 ingly we find the two upper shelves very broadly and rudely deve- 

 loped, and there are a good many waterworn stones upon them. 

 The lowest line runs along the base of the hill, and is less remark- 

 able at this point. Again, on the south-west slope of Bohuntine 

 Hill I noticed a great number of waterworn stones and pebbles at 

 and beneath the level of the lowest parallel, which is the only one 

 that occurs there. This part of the hill faces a wide opening towards 



1 Trans. Eoy. Soc. Edin. vol. ix. (1821) p. 10. 



2 Quart. Journ. Geol. Soc. vol. xix. (1863) pp. 250 & 256. 



3 Trans. Geol. Soc. Edin. vol. v. (1885) p. 268. 



c2 



