370 Dr. Mac Culloch on the Parallel Roads of Glen Roy. 



skirted by a gravelly shore, forming an inclined plane and con- 

 stituting a zone at the level of the water ; of greater or less breadth 

 according to the declivity of the hill, the quantity of alluvial matter 

 present, and the nature of other circumstances which occasionally 

 modify the action of these causes. Thus on entering a few feet 

 within such a lake on a shore of moderate inclination, we plunge 

 suddenly down, and in such a case it will be found that the sound- 

 ings which succeed to the narrow zone above described, generate 

 a section of which the line indicating the declivity is continuous with 

 that which lies similarly above the water. Wherever rocks protrude 

 on the face of a hill in such circumstances, the shore above described 

 is either altogether wanting or imperfectly marked ; according to 

 the particular inclination of these rocky faces, or according to 

 other circumstances on which it is unnecessary to dwell minutely. 

 Where the declivity is greatest, the shore is not only narrowest, but 

 its inclination is the greatest; and vice versa,\\. is most level and of 

 largest dimensions where that is least. The reader who will re- 

 cal to mind the particular description of Glen Roy, will recognize 

 all these features in the present state of the lines ; and it is scarcely 

 to be doubted, that if the sudden drainage of such a lake as I have 

 here described could be effected, its sides would present the appear- 

 ances which occur in that valley, as far at least as all the requisite 

 conditions were present. The conditions which have led to the 

 uniform appearance and prolonged extent of the lines of Glen Roy, 

 may be found in the general equality of the slope of the hills, their 

 uniform and rarely interrupted faces, and the generally equal thick- 

 ness and lubricity of the alluvial coat which covers them. Indeed 

 whenever these conditions are absent we see those anomalies which 

 on general principles we might be led to expect. It is true that I 

 have in the description pointed out other anomalies which do not 



