264 PLANTS, SEEDS, AND CURRENTS 



the waves. As far as the Turks Islands supplied direct evidence on 

 this point, it was to the effect that the aeolian rocks passed downward 

 into consolidated reef debris, consisting of coarse sand, dead shells, 

 and coral fragments, which had been thrown up on reef-rock at the 

 present sea-level. The same inference is to be drawn from the 

 observations of L. Agassiz on the islands of the Salt Key Bank. 



The Evidence supplied by Charts of Recent Changes in 

 Level in the Bahamas. — Fortunately this matter has received 

 considerable attention in one way or another. Looking at the 

 evidence supplied by the examination of old maps, particularly that 

 obtained by Mr. Tillinghast which is mentioned below, and having 

 regard to the unimportant changes that occurred between the 

 careful survey of 1834 and the time of his visit in 1893, A. Agassiz 

 concludes that " we are warranted in assuming that the configura- 

 tion of the Bahamas, as we now know them, does not differ materially 

 from that of the Y as de los Lucayos as they were first discovered by 

 Columbus." From this we may infer that during a period of 400 

 years no great change has occurred in the relations between land and 

 sea in this region. 



Mr. Tillinghast carried out his investigations with the idea that 

 " an examination of old maps " might reveal a change in the con- 

 dition of the Mouchoir, Silver, and Navidad Banks since the time of 

 the discovery of the Bahamas " which might be of importance in the 

 disputed question of the landfall of Columbus." As a result he 

 formed the conclusion, after examining a large number of old charts 

 going back to the beginning of the sixteenth century, that " they 

 throw more light on the condition of the cartography of the West 

 Indies than on any physical change among the islands " (see Notes 

 on the Historical Hydrography of the Handkerchief Shoal (Mouchoir 

 Bank) in the Bahamas, in the " Library of Harvard University, 

 Bibliographical Contributions," No. 14, 1881). 



In this connection A. Agassiz lays stress on the difficulties sur- 

 rounding such investigations, and notably the rarity of actual sur- 

 veys of these regions. He points out (p. 14) that in the chart of the 

 first survey of these three banks at the south-east end of the Bahamas, 

 that of Count de Chastenet-Puysegur (1784-7), only shoals and 

 banks are drawn. This is interesting as showing that the three 

 banks (Mouchoir, Silver, Navidad) bore no islands then as they bear 

 no island now. Their stationary condition during the last 200 

 years is also indicated by the fact that their shoals and rocks were 

 as dangerous to the navigator in the early part of the eighteenth 

 century as they are now. The site of a wreck, named " Plate 

 Wreck," is marked in some of the old charts on one or other of 

 these three banks. Thus it is shown in one of the maps given by 

 Catesby in his work on the natural history of Carolina, Florida, and 

 the Bahamas (Vol. I., 1731). 



In the British Museum library I came upon an old chart of the 

 Turks Islands, which is not included in Tillinghast' s extensive list 

 of the early maps of this region. It describes itself as constructed 

 from " a survey made in 1753 by the sloops VAigle and V Enter aude 

 by order of the French Governor of Hispaniola with improvements 



