EANGIROA. 33 



Rangiroa. 



Plates 4-19, Wl, 202 ; 20i,figs. 3, Jp ; 205, fig. 3 ; and Figs. 2, 3, 5. 



After striking Ahe we made for Rangiroa, skirting the northern shore. 

 Rangiroa' is somewhat pear-shaped (Pis. 201, 202; 204, fig. 4). Its 

 broadest part is towards the northwestern face. The northern land rim is 

 thickly wooded. The irregular arc forming the southern face of the atoll 

 is edged by the great wall of elevated reef rock ; there are but few 

 islets and islands on the sea face of the wide reef platform, which extends 

 far into the lagoon. 



About five miles eastof Tiputa Entrance (PI. 204, fig. 3) there are masses 

 of large coral rocks and boulders " at the foot of the high sand beach, which 

 cover the shore platform for a considerable distance. Steaming parallel with 

 the shore, we find these reaches of boulders alternate with clear flats of 

 the shore platform. This is about 250 to 500 feet in width from the ba.se 

 of the steep coral sand beach, which varies in height from 8 to 15 feet. 

 Occasionally the outer platform can be seen to extend in towards the lagoon 

 and to form a shallow pass from it to the outer sea across the narrow land 

 rim forming the northern side of the Rangiroa atoll. The northern land 

 rim is well wooded with masses of shrubs and low trees, and with tall 

 cocoanut trees rising to a height of from 25 to 40 feet. 



At Tiputa Pass we obtained our first glance into one of the large 

 Paumotu atolls. The entrance is a little over a cable length wide (PL 204, 

 fig. 3), and a strong current flows out during ebb- tide, running, it is said, 

 from seven to eight knots per hour. The outward flow is regulated by the 

 strength of the trades; if they force much water over the weather side of 

 the reef, it continues sometimes to flow out for several days in succession. 

 On the interior of the western side of the pass a couple of small islands (PI. 

 204, fig. 3), Nui Nui, extend, of which the base is, as we shall see, made up 

 of tertiary coralliferous limestone covered over in part with recent stratified 

 beach rock or coral breccia and conglomerate. 



' I give an account of each island and of the various groups we visited in the order in which we 

 examined them. 



* Dana mentions such large boulders as occurring at Raraka, Kauehi, Manibi, and Aratika. 



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