62 MR SMITH ON THE CHANGES 



tion from the relative size of the ancient terraces with those 

 now forming, it must have exceeded the recent period of 

 which two thousand years is but a part, by an immense 

 amount ; but this is but one of the epochs in the history of 

 this formation ; between the great terrace and the sea se- 

 veral subordinate ones and beaches have been observed, 

 each of them marking long continued periods of repose, 

 whilst a sudden deepening, two or three fathoms below the 

 low- water mark, is probably caused by another line of ter- 

 races now covered by the sea. 



The great terrace, the base of which seems very gene- 

 rally to be between 30 and 40 feet above the sea, forms 

 a marked feature in the scenery of the west of Scotland, 

 in those parts where the violence of the Atlantic has not 

 swept away the plateau of marine alluvia which, in the less 

 exposed situations, is always interposed between it and the 

 sea. 



The northern part of the county of Ayr, which is com- 

 posed of a coarse red sandstone or conglomerate, has been 

 worn by the former action of the sea into a magnificent 

 range of cliffs, in some places rising to the height of 300 

 feet ; the two islands of Greater and Lesser Cumbra, lie 

 opposite to it, and have corresponding terraces. The for- 

 mer of these islands is composed of the same sandstone in- 

 tersected by trap veins ; both the trap and sandstone have 

 been worn away, but in different degrees, and the dykes 

 are left standing out from the cliffs like ruined walls, af- 

 fording no doubtful evidence of the length of time during 

 which the sea formerly washed their bases.* 



* The time is not yet gone by with geology, as it has with astrono- 

 my, when the conclusions drawn from its phenomena are supposed to 

 be inconsistent with the word of God. I rejoice, however, to feel as- 

 sured that, in yielding to evidences which it is impossible for me to 

 resist, I am neither denying its truth, nor wresting it to my own pur- 



