Descent and Upheaval over the Northern Hemisphere. 325 



burgh and Perth. Betwixt Errol and Invergowrie Bay, on 

 the opposite shore, is a bed of cockles about three feet above 

 high- water mark, corresponding closely in character, with 

 that of Borrowstounness.* The Arbroath railway cuts and 

 exposes the shell-bed from near Dundee to Broughty Ferry, 

 after which it is concealed by the Sandy Downs. It reappears 

 to the eastward of Arbroath, and again in Lunan Bay, and 

 to the north and south of Montrose. Beyond this my re- 

 searches along shore have not extended. 



Two beaches are described by Mr A. Stevenson, off the Ross 

 of Mull, near Skerryvore,t in the Firth of Clyde, and they 

 prevail probably along much of the low part of the coast to 

 the south. J 



6. The reasons why raised beaches are not at all continu- 

 ous along our shores are very obvious. Where the shore 

 is precipitous, and the water deeper at the bottom of the 

 cliff than the whole amount of the upheaval, then, though 

 the bottom of the sea might be raised by so much, and the 

 water become to this extent shallower, there would be no 

 actual beach, and the aspect of the coast would then nearly be 

 the same as before, the cliffs having become just so much 

 loftier. Beaches, originally existing, have been swept away 

 when the whole of the material composing them consisted of 

 sand, shells, or gravel, or when they rested on rock liable to 

 decomposition, and the sea, in these cases, has once more 

 approached its former cliffs or margin. Along the shores of 

 Fife there are beautiful illustrations of beaches, well-pre- 

 served, where the rock was exposed in a way advantageous for 

 resistance, and of their disappearance where it was otherwise. 

 Near Crail the rock dips under the sea and exposes a surface 

 well suited to withstand the surge ; and there, accordingly, 

 we have extensive raised beaches with the old sea-cliffs a 

 considerable way inland. Near St Andrews, again, it is the 

 reverse of this, the rock dips away from the sea, and the up- 

 heaved beach has been worn away, the waves now attacking 

 and abrading the old sea-cliff. In this, again, ten or twenty 

 feet up the cliff, we have caves. Lady Buchan's at St Andrews, 



* Buist's Geological Survey of Perthshire. — Highland Society's Transactions^ 

 1838. 



t Jamesou's Journal, 1840. J Chambers' Old Sea-Margins. 



