TAHITI. 147 



are growing. The beaches of the bay are composed alternately of volcanic 

 or of coral sand derived partly from the cliffs and partly from the coral 

 patches. 



Although the prevailing trade is from the southeast, the wind during the 

 fall and the beginning of winter is more from the eastward, and in the early 

 winter it varies between northeast and northwest; the condition of the reef 

 flats along the shores of Tahiti shows how dependent the topography of 

 the reefs is upon the prevalence of winds from certain dii'ections. The 

 swell which comes from the northeast and east has eroded the wide barrier 

 reef lagoon between Mahaena Pass and Point Venus; the northeasterly and 

 westerly winds have eroded the platform of Matavai Bay, and h.ave to a 

 great extent directed the currents which have formed the liarbor of Papiete 

 and the extension of its lagoon to the east and to the west. 



The prevailing trades rake the east coast of the peninsula and of the 

 main island, and have reduced the outer edge of the reef platform to a 

 narrow barrier reef. On the southwest and the west faces, which are pro- 

 tected from the prevailing winds and from the variable winds, we have wide 

 barrier reef platforms still fairly extant, joined with the shore by innumer- 

 able coral reef patches. From the expansion of these patches the barrier 

 reef platform passes more into what we may call fringing reefs or fringing 

 reef flats of considerable width ; the fringing reef flat off Hapaa (PL 208, 

 fig. 5) being more than a mile wide, and the outer edge of the barrier reef 

 platform off the northwest point of Tahiti being fully one and a half miles 

 from shore. To the east of Papara the reef flat, both barrier and fringing, 

 is, in some points, nearly one and three-quarters miles wide. The reef flats 

 south of Port Phaeton are also marked for their great width. Off the north 

 face of Tahiti the reef flat which once existed between Artemise Bank and 

 Point Venus must also have been of great width, judging from the outliei's 

 of its outer edge which are still left standing. Tidal currents of consider- 

 able velocity flow out through all the narrow reef passes of the northwest, 

 southwest, and south coast of Tahiti. These currents are also reinforced by 

 the mass of water which pours down the hillside during the rainy season. 

 On the east coast the passes are of considerable width and much greater 

 depth, and there is no such concentrated flow as is noticed on the west 



