PRELIMINARY REPORT. ay 
as the Ellice and Gilbert, seem to be somewhat higher than the Paumotus, 
but this difference is only apparent, and is due to the difference in the 
height of the tides, which is very small in the Paumotus, while in the 
former groups it may be five, and even six feet. 
From Jaluit we visited among the Carolines, the islands and atolls of 
Kusaie, Pingelap, Ponapi, Andema, Losap, Nama, the Royalist Group, 
Truk, and Namonuito, obtaining thus an excellent idea of the character 
of, the high voleanic islands of the group from our examinations of Kusaie 
and of Ponapi, while the others represent the conditions of the low atolls, 
having probably a volcanic basis, but this was not observed at any of 
those we examined. 
The reefs of the volcanic islands of the Carolines are similar in char- 
acter to those of the Society Islands, though there are some features, 
such as the great width of the platforms of submarine erosion of Ponapi 
and of Kusaie, and the development of a border of mangrove islands at 
the base of the volcanic islands, which are not found in the Society Islands. 
The Truk Archipelago was perhaps the most interesting of the island 
groups of the Carolines, and it is the only group of volcanic islands sur- 
rounded by an encircling reef which I have thus far seen in the Pacific 
which at first glance lends any support to the theory of the formation of 
such island-groups as Truk by subsidence. This group was not visited 
by either Darwin or Dana; and I can well imagine that an investigator 
seeing this group among the first coral reefs would readily describe the 
islands as the summits, nearly denuded, of a great island which had 
gradually sunk. But a closer examination will readily show, I think, 
that this group is not an exception to the general rule thus far obtaining 
in all the island groups of the Pacific I have visited during this trip; 
that we must look to submarine erosion and to a multitude of local 
mechanical causes for our explanation of the formation of atolls and of 
barrier and encircling reefs, and that, on the contrary, subsidence has 
played no part in bringing about existing conditions of the atolls of the 
South and Central Pacific. 
Nowhere have we seen better exemplified than at Truk how important 
a part is played by the existence of a submarine platform in the growth 
smn ime meio 
