172 CORALS AND CORAL ISLANDS. 
Near the eastern end of Metia, an island nearly north of 
Tahiti, 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 of the shore reef, the water slowly deepens, and 
then there is an abrupt descent at an angle of 40 or 50 
degrees. The results of earlier voyagers correspond with 
this statement. 
Beechey, whose observations on soundings are the fullest 
hitherto published, states many facts of great interest. At 
Carysfort Island, he found the depth, 60 yards from the surf 
line, 5 fathoms; 80 yards, 15 fathoms; 120 yards, 18 fath- 
oms; 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, 500° feet 
out, there was no bottom at 1,500 feet. 
Darwin states other facts bearing upon this subject, of 
which we may cite the following: At Heawandoo Pholo (one 
of the Maldives), Lieutenant Powell found 50 or 60 fathoms 
close to the edge of the reef. One hundred fathoms from the 
mouth of the lagoon of Diego Garcia, Captain Moresby found 
no bottom with 150 fathoms. At Egmont Island, 50 fath- 
oms from the reef, soundings were struck in 150 fathoms, At 
Cardoo Atoll, only 60 yards from the reef, no bottom was ob- 
tained with a line of 200 fathoms. Off Keeling Island, 2,200 
yards from the breakers, Captain Fitzroy found no bottom 
at 1,200 fathoms. Mr. Darwin also states that, at a depth 
between five and six hundred fathoms, the line was partly 
cut as if it had rubbed against a projecting ledge of rock; 
and deduces from the fact “the probable existence of sub- 
marine cliffs.” 
