38 EXPEDITION OF THE "ALBATROSS," 1899-1900. 



of coral reefs. The encircling reef protects the many islands of the 

 gioup against a too rapid erosion, so that they are edged by narrow 

 fringing reefs, and nowhere do we find the wide platform so essential to 

 the formation of barrier reefs. The effect of the northeast trades blowing 

 so constantly in one direction for the greater part of the year is of course 

 very great ; the disintegration and erosion of islands within its influence 

 is incessant, and their action undoubtedly one of the essential factors in 

 shaping the atolls of the different groups, not only according to the local 

 position of the individual islands, but also according to the geographical 

 position of the groups. Thus far I do not think any observer has given 

 sufficient weight to the importance of the action of the trades in modify- 

 ing the islands within the limits of the trades; nor has it been noticed 

 that the coral reefs are all situated practically within the limits of the 

 trades, both north and south of the equator. It is interesting to note 

 that there are no coral reefs in two extensive island groups of the 

 Pacific, the Marquesas and the Galapagos, both within the tropics in the 

 same latitudes where far to the westward the Gilbert and other Line 

 islands, as well as the Ellice and Solomon Islands, are noted for the abun- 

 dance of corals and the great development of coral reefs. At tlie Galapagos 

 and Marquesas, corals exist only in patches, forming short stretches of 

 fringing reefs, and. it is difficult to account for the absence of coral reefs 

 in these groups except on the supposition that the shores are usually too 

 steep, that no great platforms of submarine erosion flank the islands, and 

 finally that the shore cliffs and slopes are reailily disintegrated by the 

 action of the sea and afford no permanent foothold to growing corals. 



The soundings made going west from Jaluit to Namonuito indicate 

 that tliere is no great plateau from which the Carolines rise, but that the 

 various groups are, as is the case witli the neighboring groups of the 

 Marshalls and Gilberts, isolated peaks with steep slopes rising from a 

 depth of over 2000 fathoms. The line wo ran from the northern end of 

 Namonuito to Guam developed the eastern extension of a deep trough 

 running south of the Lad rones. The existence of this trough had been 

 indicated by a sounding of 4475 fathoms to the southwest of Guam 

 made by the "Challenger." We obtained, about 100 miles soutlieast of 



