ACTION OF THE SEA UPON COASTS. 379 



origin to the destroying agency of the ocean at a former 

 period, are again yielding to its action. At Saint An- 

 drew's, the famous castle of Cardinal Beaton, which is 

 said originally to have been some distance from the sea, 

 now almost overhangs it : From St Andrew's northward 

 to Eden water and the River Tay, the coast presents a 

 sandy beach, and is so liable to shift, that it is difficult 

 to trace the change it may have undergone. It is cer- 

 tain, however, that, within this last century, the sea has 

 made such an impression upon the sands of Barrey, on 

 the northern side of the Tay, that the light-houses at 

 the entrance of the river, which were formerly erected 

 at the southern extremity of Button-ness, have been 

 from time to time removed about a mile and a quarter 

 further northward, on account of the wasting and shift- 

 ing of these sandy shores, and that the spot on which the 

 outer light-house stood in the 17th century, is now two 

 or three fathoms under water, and is at least three quar- 

 ters of a mile^within flood-mark. 



NOTE, p. 32. 



On the growth of Coral Islands. 



OF all the genera of lithophytes, the madrepore is the 

 most abundant. It occurs most frequently in tropical 

 countries, and decreases in number and variety as we ap- 

 proach the poles. It encircles in prodigious rocks and 

 vast reefs many of the basaltic and other rocky islands in 

 the South Sea and Indian Ocean, and, by its daily 

 growth, adds to their magnitude. The coasts of the is- 

 lands in the West Indies, also those of the islands on 

 the east coast of Africa, and the shores and shoals of the 

 Red Sea, are encircled and incrusted with rocks of coral. 



