368 ARRAN. GEOLOGY. SECONDARY STRATA. 



In the general description of the island, I have men- 

 tioned the picturesque features of an avalanche of rock 

 occurring on the northern shore. That spot is the central 

 point from which this account commences. The name 

 of the place is, I believe, Scriden, but the circumstance 

 now described will furnish a mark less liable to be mis- 

 taken. An immense mass, consisting chiefly of red 

 sandstone conglomerate, is here seen reaching to a 

 great height in the hill, and occupying an extensive 

 tract along the shore. Its thickness may be estimated 

 at 800 or 1000 feet; although it should be much less 

 it is an error of no moment. It is impossible for a consi- 

 derable space to determine whether this mass has any 

 dip or not where it lies on the sea shore, at least if a 

 wide view be taken.* For such a view the spectator 

 is supposed to stand at an indefinite distance in front 

 of this point, and towards the N. E. ; the only inclination 

 at present under consideration being that which relates to 

 the strata lying on the shore, and which respects the north- 

 west and south-east points, or those at right angles to 

 the spectator's position. It is evident that the position 

 of the strata against the mountain, will cause a dip 

 towards him in the upper portions, as shown in one 

 of the diagrams ; but this does not affect the present 

 question ; while it is obvious that these portions also must 

 be affected in the same way as the lower, as far as the 

 form of the high land permits.t If from this place, 

 where there is no dip to either of the points just men- 



* It has elsewhere been noticed, and is here important to recollect, 

 that general conclusions can rarely be drawn from partial and nice 

 examinations of the dips of strata. I may indeed add, that the more 

 accuracy the more error; a rule strongly exemplified here, as well as in 

 other places where, from undulations or fractures, they waver in every 

 direction. 



f Although the contemplation of the several diagrams will assist 

 the reader's comprehension, nothing short of a model could represent 

 accurately the dispositions of the several strata, or the general form 

 of the mass. 



