316 "ALBATROSS" TROPICAL PACIFIC EXPEDITION. 



sides of the passage, the position of the submerged reef, the dark blue grad- 

 ually passing into a lighter blue, finally into a bluish green, a yellowish or 

 even light green ; the edges of the passage being covered with patches of 

 the peculiar iridescent and metallic coloring we have mentioned before. 

 This band of highly colored water seen in the morning and evening sun 

 seems to be characteristic of the Marshall Islands ; we did not observe 

 it, or saw it only on a very limited scale, in any of the other atolls 

 we visited. 



Passing out of Rurick Pass, we followed the narrow submerged reef line 

 of the lee face of Wotje atoll marked by its light green color, interrupted 

 here and there by an occasional islet or breaker. The tide at the Marshall 

 Islands rises from five to seven feet, so that the amount of water which is 

 daily poured over the reef flat into the lagoon must be enormous. In 

 addition this mass of water is driven by the trades, so that a very different 

 condition exists from that of the Paumotus, where although there is a 

 powerful swell, yet the tides are comparatively insignificant, the southeast 

 trades are moi'e or less interrupted, and the passes are few in number a,nd 

 usually narrow. The amount of water entering into the atolls of the 

 Paumotus bears no comparison to the rush of water entering into many 

 of the other atolls of the Pacific. 



The first island to the eastward of Rurick Pass was well wooded, although 

 but a narrow thread of land. It was edged on the sea face with beach rock 

 conglomerate, the two extremities of the island forming sand spits, the sand 

 having been driven from the lagoon beach and overwhelming little by little 

 the beach rock conglomerate which crops out upon the reef flat (PI. 228, 

 fig. 1). This island is crowded with terns and forms a gigantic rookery. 

 To the eastward another islet is thrown up on the half-submerged reef flat. 

 To the south of these crop out occasional stretches of coral sand raised 

 slightly above the level of the reef flat. There is considerable swell on the 

 southern face of the atoll, and a long line of breakers indicates the posi- 

 tion of the outer half-submerged reef flat. Many of the islands and islets 

 near Schischmarev Pass (PI. 180, fig. 2) are only reaches of beach rock 

 conglomerate pounded by the breakers. At the angle of the southern face 

 of the atoll leading to Schischmarev Pass a large island has been formed ; 



