68 



EXCURSION II. 



THE CORRIEGILLS SHORE. 



34. TO-DAY we shall stroll leisurely by the sea-side, and 

 study the eruptive rocks which break through the Corriegills 

 sandstone. The botany of the shore is rich, and the pools in 

 the tide-way teem with life. We shall notice in this place 

 the geological phenomena only. A group of whin dikes marks 

 the first emergence of rock from beneath the Brodick sands ; 

 and from this point eastwards the rocky platform exhibits a 

 complete network of interlacing veins and beds of igneous 

 products, traversing the sandstone strata. Between the end 

 of the sandy beach and the landing-pier at Spring-bank there 

 are several cases of bifurcation of dikes, and of a singular 

 crumpling of the sandstone strata. The bed of the burn 

 within the pretty grounds connected with the hotel shews 

 several greenstone dikes, and the beds of sandstone are well 

 seen in the banks and rocky ledges over which the water 

 tumbles. On the shore fine sandstone and conglomerate are 

 irregularly intermixed, indicating periods of sudden and gra- 

 dual deposit, and varying forces in the transporting currents. 

 The sandy strata are red, yellow, and white, and, as we ad- 

 vance eastwards, predominate over those of conglomerate 

 structure. The fragments in the conglomerate are mica 

 slate, like that of Can tire, slate similar to that of the nucleus, 

 white quartz, and quartz of that peculiar resinous variety 

 (Art. 7), for which we know no locality in Arran. Pieces of 

 porphyry also occur, but no fragments of granite. The whole 

 series dips nearly south, at angles varying from 15 to 20. 

 The upper surface of the sandy beds is worn in a singular 

 way, portions more quartzose, or with a calcareous cement, 

 standing out in thin, sharp, irregular ridges, while the parts 



