* 
66 Natural History of Fanning’s Group.  [February, 
row, shallow channels, through which the water of the ocean 
finds free access to the lagoons. In a completed atoll the rim 
of land inclosing the lagoon is unbroken, but in the greater num- 
ber of coral ilanda a narrow lagoon-outlet is always found on 
the western side. 
A broad, interior shore platform of fine coral sand extends, in 
places, from one side of the island to the other, and forms dis- 
tinct boundaries for the lagoons, and connects together most of 
the islets. It also forms a barrier to the westward, approximat- 
ing the two extremities of the horseshoe, leaving the lagoon-out- 
lets so very narrow and shallow as hardly to admit of the passage 
of aship’s boat. The outer shore platform is about three hun- 
dred feet wide, and is covered with coarse coral blocks. 
The island is being gradually extended to the westward. 
From the two ends of the horseshoe the water breaks out for a 
mile or more, and from the northern end it shoals around ina 
curve to the southward for three or four miles. This, too, in 
years to come, will be elevated above the surface and another 
body of water will be inclosed, forming a lagoon where vessels 
now ride at anchor. 
Very scanty evidence of any agents having been at work in 
building up the land other than the coral animal and the action 
of the waves are observable anywhere about the island. The 
highest point is only seven feet above high water. In no place 
has the reef-rock been upheayed. But an elevation of a few 
inches might be supposed from the position of the rock of beach 
formation, which in places has been lifted up horizontally out of 
the reach of the tides. 
The eastern islets are the oldest in formation. That this is 
true is evident from several facts. In the first place, the vegeta- 
tion there is denser and ranker, and more genera are represented 
than on the islets to the leeward. All the plants that were found 
growing on the latter islets also exist on the eastern, with the 
addition of several species that have not yet been diffused to the 
westward, showing that the germs of life started into existence 
in the east, the direction of the prevailing wind and current. 
further proof of this is shown in the condition of the cocoanut- 
trees in the different localities. This tree when young is bulb- 
ous at the base, a condition which is observable in all the trees 
on the western islets, while on, those to the windward they are 
taller and the trunks have nearly the same diameter from the 
base to the crown. 
