§45. DRIFTED SAND. 91 



being hatched, are preserved. The conglomerate of the 

 Isle of Ascension is, as you may observe, principally com- 

 posed of corals. Here we have another example of a rock 

 formed of the calcareous skeletons of those wonderful forms 

 of organic existence ; but it is not my intention in this place 

 to dAvell on the geological changes produced by zoophytes 

 in the formation of coral reefs, &c, as the examination of 

 the recent and fossil corals will form the subject of a 

 subsequent Lecture. 



45. Drifted sand. — We have already alluded to the 

 encroachments on the land by the drifting of sand-banks 

 thrown up beyond the reach of the tide, and driven by the 

 winds inland ; thus effecting the desolation of whole regions 

 by their slow, but certain progress. Egypt instantly pre- 

 sents herself to the imagination, with her stupendous 

 pyramids, the sepulchres of a mighty race of monarchs, 

 and the wonder of the world — her temples, and palaces, 

 once so splendid and massive, as to bid defiance to the 

 ravages of time — her plains, and valleys, formerly teeming 

 with abundance, and supporting a numerous population — 

 now stripped of her ancient glories, her fairest regions 

 depopulated, and converted into arid wastes, — her cities 

 overwhelmed, and prostrate in the dust— and the colossal 

 monuments of her kings, and the temples of her gods, half 

 buried beneath the sands of the Desert ! 



The drifting of the sands of the Lybian desert by the 

 westerly winds, observes M. De Luc, has left no lands 

 capable of cultivation on those parts of the western bank 

 of the Nile which are not sheltered by mountains ; while 

 in Upper Egypt, whole districts are covered by moveable 

 sands, and here and there may be seen the summits of 

 temples, and the ruins of cities which they have over- 

 whelmed. " Nothing can be more melancholy," says 

 Denon, " than to walk over villages swallowed up by the 

 sand of the Desert, to trample under foot their roofs and 



