RASAY. GEOLOGY. 253 



characterized by the presence of large balls, which are 

 seen standing out on the faces of the cliffs, or lying 

 on the shore resisting the action of the weather long 

 after the surrounding parts have decayed. These con- 

 cretions are equally common in Sky and in Egg : they 

 do not appear to differ in composition from the sur- 

 rounding substance, but are too well known to geologists 

 to require a detailed description. Large balls of trap 

 occur also in the sandstone, but more rarely. The 

 surfaces of these are always decomposed, and they 

 bear evident marks of having undergone attrition before 

 they were deposited in their present situations. Besides 

 these different substances, there are found pedunculated 

 ferruginous bodies resembling Pezizae, and doubtless ap- 

 pertaining to the family of alcyonia. 



Before dismissing this rock I must take notice of an 

 irregular portion which is seen on the western side of 

 the island at the junction of the red sandstone. It is of 

 small extent, but instead of lying on that rock in the usual 

 conformable order, it is placed on its elevated edges and 

 dips to the eastward of south, being, consequently, uncon- 

 formable to the principal mass. Such appearances are not 

 usual among the secondary strata, but, as the porphyry 

 occurs here, it is probably an irregularity proceeding 

 from the intrusion of that substance. I shall not attempt 

 further to describe those portions which appear in various 

 parts of the island, as if detached from the main body. 

 This is often a fallacy arising from the intricate form of 

 the ground and from the covering of vegetable soil: 

 in some cases it is the result of the trap and porphyry, 

 which either cover the uppermost beds or interfere with 

 the whole by intersecting them. 



It is now necessary to take a short retrospect of 

 the strata from the red sandstone upwards. 



The limestone which occurs at Broadford immediately 

 on that rock, and will be amply described hereafter, 

 contains the same organic remains that are found in the 



