38 EXPEDITION OF THE “ALBATROSS,” 1899-1900. 
of coral reefs. The encircling reef protects the many islands of the 
group 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 Ido 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 the 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 readily 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 there is no great plateau from which the Carolines rise, but that the 
various groups are, as is the case with the neighboring groups of the 
Marshalls and Gilberts, isolated peaks with steep slopes rising from a 
depth of over 2000 fathoms. The line we ran from the northern end of 
Namonuito to Guam developed the eastern extension of a deep trough 
running south of the Ladrones. 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 southeast of 
