270 PLANTS, SEEDS, AND CURRENTS 



the area occupied by the present archipelago ; but, judging from the 

 size of the larger banks, several of the islands must have been as 

 large as an ordinary English county. In addition to the original 

 islands of seolian formation, of which fragments still remain, there 

 were several others, of which no trace now remains beyond the 

 submerged bank that has been generally worn down to the lower 

 limit of breaker-action, except where it displays a few " rocks awash." 

 Probably none of the islands exceeded 500 feet in elevation, and 

 their average height must have been less than half this amount. 

 Their entire surfaces were covered by wind-blown sand; and, in 

 fact, their entire thickness was the work of the drifting dune. The 

 compacted aeolian formations, of which they are now composed from 

 top to bottom, plainly tell the story of the building up of these 

 islands; and there is little to indicate that there was any covering 

 of vegetation of any extent. 



The History of the Bahamas is the History or the Sand- 

 dune. — These large islands were built up under the sway of the 

 shifting sand-dune, and must have offered a spectacle not to be 

 found on the same scale in any insular territory in the present era, 

 not even in the great coral-reef regions of the Indian and Pacific 

 Oceans. These unusual formations, unusual in the sense just 

 defined, required unusual conditions; and we have now to ask 

 ourselves what exceptional conditions offered the opportunity for 

 the dominion of the dune. 



They must have been the conditions that prevail on the sea-board 

 of those great continental masses where the dune holds its sway. 

 At the present time the most insignificant sandbank in coral seas 

 becomes the home of the mangrove, and numerous other plants 

 establish themselves as the bank emerges from the waves. We do 

 not read in our own day of islands in coral seas that are swept clean 

 by ever- shifting sand-dunes. The Turks Islands lie in a region of 

 storms and gales ; and if ever strong winds could restore the original 

 sterility of these islands we might look for their work here. Yet, 

 what do we find ? In an island like Salt Cay, where the sand-dunes 

 are well developed in places, they make but little effort to overrun 

 the surface. The conditions of the present are confessedly not 

 those of the past ; and in what, we may ask, has been the change ? 



Before answering this question, let us picture to ourselves the con- 

 ditions that once prevailed over insular land- areas, fifty to a hundred 

 miles across, where the drifting sands reigned supreme, conditions 

 that, as above remarked, are now only found on the sea-board of 

 great continents. The coast regions of Peru are the home of the 

 shifting sand-hill, or " medano," so graphically described by Dr. von 

 Tschudi in his Travels in Peru (London, 1847, p. 243). A fine light 

 yellow drift-sand here covers hill and dale, and when driven by 

 violent winds the medanos pass rapidly over the sandy plains. The 

 smaller ones, though moving quickly forward before the larger ones, 

 are soon overtaken and overwhelmed by them. At one time they 

 cover the plain. At another they move across its breadth in rows. 

 The whole face of the landscape may in this manner be transformed 

 in a few days, and the traveller who had previously lost his way 



