68 ' CORAL FORMATIONS. 
The surface of the island is singularly rough, owing to erosion by 
rains. ‘The paths that cross it wind through narrow passages among 
ragged needles and ridges of rock as high as the head, the peaks and 
narrow defiles forming a miniature model of the grandest Alpine 
scenery. There is but little soil, yet the island is covered with trees 
and shrubbery. 
The shores, at the first elevation of the island, must have been worn 
away to a large extent by the sea; and the cliff and some isolated 
pinnacles of coral rock still standing on the shores are evidence of 
the degradation. But at present there is a shore platform of coral 
reef, two hundred or two hundred and fifty feet wide, resembling 
those of the low coral islands, and having growing coral as usual 
about its margin, and in the shallow depths beyond. 
In the face of the cliff there are two horizontal lines, along which 
cavities or caverns are most frequent, which consequently give an 
appearance of stratification to the rock, dividing it into three nearly 
equal layers. 
We might continue our account of coral reefs and islands, by 
particular descriptions of those visited by the Expedition. But the 
similarity among them is so great, and their peculiarities are already 
so fully detailed, that this would amount only to a succession of 
repetitions. And moreover the facts will be found in the geographical 
report by Captain Wilkes, and are to a great extent well exhibited on 
the map of the Paumotus and on the other valuable charts of the 
Expedition. ‘The characters of a few briefly stated will suffice in 
this place. We commence with the smallest. 
Jarvis’s Island. (Fig. 4, page 53.) Lat. 0° 22’ S. Long. 159° 
31’ W. Length 13 miles, trending east and west. No lagoon. Shape 
triangular. A low sandy flat, eighteen or twenty feet high, without 
his work on Missionary Enterprises in the Pacific, gives very interesting descriptions of 
caverns in the elevated coral rock of Atiu, one of the Hervey Group.* In one, he 
wandered two hours without finding a termination to its windings, passing through 
chambers with “ fretwork ceilings of stalagmite and stalactite columns, which, ’mid the 
darkness, sparkled brilliantly with the reflected torch-light.” This author remarks, ‘“ that 
while the madrepores, the brain, and every other species of coral are full of little cells, 
these islands, (including those resembling Atiu,) appear to be solid masses of compact 
limestone, in which nothing like a cell can be detected.” 
Beechey, in his description of Henderson Island, another of this character, speaks of 
the rock as compact, and having the fracture of a secondary limestone. 
* Wateoo of Cook. 
