EXCURSION I. 51 



Invercloy shore, and extends far up both sides of Glen Cloy. 

 The lower part of the glen, much of the plain of Brodick, 

 and the marshy grounds at the head of the bay, are but an 

 expansion of the terrace which formed the sea bottom when 

 the tides and waves were carving out the cliff. The alluvium 

 and rolled stones form, however, but a thin covering to the 

 subjacent sandstone, which appears in the river bed a little 

 way up the glen. It appears also in the bed of the Rosa 

 burn, but nowhere in the Brodick plain. This plain, indeed, 

 is but an old expansion of the beach. The bay formerly 

 had its termination some way up Glen Rosa. The mound 

 in front of the glen, on which a farm-house lately stood, is 

 but forty feet above high water ; the mouth of Glen Rosa is 

 much less; in fact, it is quite within the limits, to a con- 

 siderable distance up, of the old sea terrace. Brodick plain 

 shews beneath the soil a continuous covering of rolled gravel 

 cemented by iron, and impervious to water. To drain it in 

 any part, it is only necessary to pierce this covering, when 

 the water at once disappears. On the north-west of Glen 

 Cloy the sandstone is quarried upon the line of cliff, and 

 forms a tolerable building stone. The dip is nearly south, 

 at about 25. By the side of Brodick wood, adjoining the 

 neat school-house erected by the late Duke of Hamilton, 

 a vein, or perhaps bed, of pitchstone occurs in the sand- 

 stone. A portion only of the front appears by the side 

 of a lane, shewing a prismatic structure in the rock, and an 

 underlie towards the west. In large blocks lying loose upon 

 the surface, a similar structure is seen. The colour is bottle- 

 green, and specks of red felspar disseminated in the base give 

 the rock a porphyritic texture, approaching that of pitch- 

 stone porphyry. The direction is nearly south-east and 

 north-west. It is probably a continuation of one of the 

 many beds or veins of the Corriegills shore, which we shall 

 notice in another Excursion. A breadth or width of fully 

 thirty yards is exposed ; but it is very difficult to say whether 

 it is a bed or a vein. We were unable to trace it north- 



