292 "ALBATROSS" TROPICAL PACIFIC EXPEDITION. 



of islands and islets on the land rim of the northeastern face of the atoll. 

 We could also see across the western land rim, near the northern extremity, 

 the line of breakers indicating the position of shoals and islets, and low 

 sand bars heaped up across the gaps of that part of the atoll, or indi- 

 cating the position of a former land rim worn down by the action 

 of the trades sweeping across from the eastern face of the lagoon. North 

 of the centre of the western face of Jaluit is a marked secondary lagoon 

 (PI. 226, fig. 6) formed as have been formed the secondary lagoons of 

 Taritari and of Apaiang. Here, however, the secondary lagoon has been 

 formed by the throwing up of islands and islets and spits on the lagoon 

 face of the land rim, the sea sweeping across the lagoon with sufficient 

 force to build up on the lagoon face of the lee side secondary lagoons 

 such as usually characterize the weather face of other atolls. More to the 

 north a similar secondary lagoon exists at Ngain, where, however, it only 

 forms a small bay. 



The sand bars and flats encroaching upon the lagoon of the north- 

 western horn of Jaluit indicate the method by which the horn of an atoll 

 may gradually be changed into a great sand spit by filling the space between 

 the land rims on the two faces of the atoll. Only a narrow gap, with a 

 shallow entrance into the atoll, exists at the northern end of Jaluit. From 

 the island of Urbett across to the west face of the atoll the lagoon is 

 not more than four miles in width ; the two faces of the lagoon extend 

 northward in a nearly parallel line, a distance of about twelve miles, 

 forming at the northern extremity a wide horn between the island of 

 Boggenadick and Bogenaga. The west face of the atoll, with the excep- 

 tion of Pinglapp, which forms the western spit of the atoll, and of the 

 secondary central lagoons, is edged by a narrow reef flat, the greater part 

 of it bare at low water, with a few islands and islets thrown up on its 

 face (PI. 226, flg. 6). 



Immediately south of the island of Boggenadick, as well as east of 

 Pinglapp and at the southern horn of Jaluit, extensive flats have formed on 

 the lagoon face of the reef, where coral patches grow in profusion or sand 

 bars have been thrown up, as also in the central part of the west face of 

 the atoll at a distance of about eight miles north of Pinglapp, where the 



