A. Agassis — Expedition to the Maldives. 307 



time, the lagoons of these atolls are far less subject to oceanic 

 circulation than those of the northern plateaus, and thus we 

 find fewer banks or islands in the lagoons and only here and 

 there a trace of those remarkable rings which are so character- 

 istic a feature in Maldivian coral reef scenery. Certainly I 

 have seen nothing so striking in my experience of coral reefs 

 as these rings with a light-colored rim standing out from the 

 deep blue water surrounding them like ghosts of an atoll, 

 which had sunk, and enclosing a lighter blue or emerald 

 colored lagoon indicative of its depth below the surface. 



The conditions existing at the Maldives is repeated to a cer- 

 tain extent on the Yucatan Plateau where the Alacran reef — 

 a regular atoll — rises from the plateau at a depth of about 30 

 fathoms. It is true that it is the only atoll on this extensive 

 plateau. But there are also other irregularly-shaped patches 

 of coral reefs. The absence of atolls may be traced to the fact 

 that the plateau is not within the area of such regular trades 

 as are the northeast and southwest monsoons in the region of 

 the Maldives. 



The strength of the prevailing winds in the Maldives has 

 greatly influenced many of the characteristic features of its 

 atolls. The effect of the southwest and of the northeast mon- 

 soons cannot be compared to that of the trades in the Pacific. 

 We have nothing in the Maldives corresponding to the inces- 

 sant breakers of the huge rollers which pound upon the reef 

 fiats of the Paumotus and of the atolls and barrier reefs of the 

 Central and Western Pacific. The boulders thrown "upon the 

 reef flats are mere pigmies compared to the gigantic masses 

 moved on some of the reef flats of the Pacific reefs. The 

 boulder belts seem like a newly-macadamized road as compared 

 to the quarry blocks which often line miles of the beaches of 

 the Pacific atolls. But the same forces are at work in the 

 Maldives only on a diminutive scale even during the prevalence 

 of the southwest monsoon. The beaches are as a whole 

 remarkably steep, both sand and shingle ; they rarely rise to 

 more than five or six feet, though in some of the northern 

 atolls they are fully 12 feet high. Mr. Gardiner informs me 

 he has seen dunes rising to 28 or 30 feet in height. Many of 

 the islands have sinks occupying the central portion of the 

 island ; they have all been formed by the enclosure within the 

 outer and higher sand or shingle beaches of the interior part 

 of the island. The beaches have been gradually raised until 

 they met the belt of vegetation which prevented the sand 

 from raising the interior part of the island. 



Wherever reef-rock was examined I found it without excep- 

 tion of the most modern character, a few exposures as horses 

 on the beaches and on the reef flats would seem to indicate a 

 slight elevation of the Maldives. The horses or outliers were 

 deeply undercut, pitted and honeycombed, showing that they 



