1850.] over the Northern Hemisphere. 305 



sion.* These beaches, which have from St. Andrew's to Ferry point 

 on Craig been covered with drift sand, re-appear along the banks of the 

 Tay — from this westward by Newburgh and Perth. Betwixt Errol and 

 Invergourie Bay on the opposite shore, is a bed of cockles, about three 

 feet above high-water mark, corresponding closely in character with 

 that of Borrowstoun Ness.j- 



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 re-appears to the eastward of Arbroath, and again in Lunar 

 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,J on the Frith of Clyde, and probably along much of 

 the low part of the coast to the south. § 



The reasons why raised beaches are not at all continuous along our 

 shores, are very obvious. Where the shore was 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 

 emergence, and the aspect of the coast would then be nearly the same 

 as before — the cliffs having become just so much loftier. Beaches, ori- 

 ginally existing, have been swept away where the whole of the material 

 composing them consisted of sand, shells, or gravel, or where 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 preserved, where the 

 rock was well exposed in a way advantageous for resistance, and of 

 their disappearance, where it was otherwise. 



* Chambers's Old Sea Margins. — For the sake of brevity I have been compelled 

 to speak very generally : it is the lowest and most recent of the Sea Margins with 

 which I am dealing. 



f Buist's Geological Survey of Perthshire.— Highland Society's Transactions, 1838. 



X Jamieson's Journal, 1840. 



§ Chambers's Old Sea Marigins. 



