CORAL ISLANDS. 5A 
ebbing tide. At Depeyster Island, it was found to run at the rate of 
two and a half miles an hour. It was as rapid at Raraka, in the 
Paumotus, and as Captain Wilkes remarks, it was difficult to pull a 
boat against it, into the lagoon. 
Soundings about Coral Islands—The water around coral islands 
deepens as rapidly and in much the same way as off the reefs about 
high islands. The atoll usually seems to stand as if stilted up in a 
fathomless sea. The soundings of the Expedition afford some interest- 
ing results. 
Seven miles east of Clermont Tonnerre, the lead ran out to 1145 
fathoms (6870 feet), without reaching bottom. Within three quarters 
of a mile of the southern point of this island, the lead, at another throw, 
after running out for a while, brought up an instant at 350 fathoms, 
and then dropped off again and descended to 600 fathoms without 
reaching bottom. On the lead, which appeared bruised, a small piece 
of white coral was found, and another of red; but no evidence of 
living zoophytes. On the east side of the island, three hundred feet 
from the reef, a bottom of coral sand was found in 90 fathoms ; at one 
hundred and eighty feet, the same kind of bottom in 85 fathoms; at 
one hundred and thirty feet, a coral bottom in 7 fathoms ;—and from 
this it decreased irregularly to the edge of the shore reef. 
Off the southeast side of Ahi (another of the Paumotus), about a 
cable’s length from the shore, the lead after descending 150 fathoms, 
struck a ledge of rock, and then fell off and finally brought up at a 
depth of 300 fathoms. 
Two miles east of Serle’s Island, no bottom was found at 600 
fathoms. 
A mile and a half south of the larger Disappointment Island, there 
was no bottom at 550 fathoms. 
Near the eastern end of Metia, no bottom was found with a line of 
150 fathoms; and a mile distant, no bottom was reached at 600 
fathoms.* In general, for one to five hundred yards from the margin 
* Beechey, whose observations on soundings are the fullest hitherto published, states 
many facts of great interest. At Carysfort Island, he found the depth sixty yards from 
the surf line, 5 fathoms ;—80 yards, 13 fathoms ;—120 yards, 18 fathoms ;—200 yards, 
24 fathoms; and immediately beyond, no bottom with 35 fathoms, At Henderson’s 
Island, soundings continued out 250 yards, where the depth was 25 fathoms, and then 
terminated abruptly. Off Whitsunday Island, 500 feet out there was no bottom at 
1500 feet. 
Darwin states many facts bearing upon this subject, of which we may cite the follow- 
