OF THE TONGA OR FRIENDLY ISLANDS. 161 
in the direction of New Zealand. In the interval between its 
southern limit and those islands is another shoal area, on which 
the small volcanic Kermadec Islands are situated. It has been 
pointed out that the volcanoes of the Kermadec and Tonga 
Islands continue the direction of those of the Taupo zone of 
volcanoes of the North Island of New Zealand. To the east of 
the Tonga plateau the sea-bottom descends to 4530 and 4429 
fathoms, the greatest measured depths in the southern hemi- 
sphere. Between Tonga and Fiji there is a depth of 1500 
fathoms. 
At the close of the last century the Tonga Islands appear to 
have been thickly populated and extensively cultivated. At the 
present time the population has greatly decreased, and much of 
the cultivated land has passed into a wild state. 
The higher part of the island of Hua presents a vegetation 
of a different character from that met with in the adjoining 
islands. 
This island, which is rather more than twelve miles long, is 
composed of a basis of volcanic tuffs overlain by reef-formation. 
On the high ridge of the island the limestone appears in isolated 
masses and pinnacles, which stand out above the red volcanic 
soil, while in the lower part it forms wide terraces at different 
levels, the upper ones ending in lines of inland cliffs. The 
eastern side, presented to the trade wind, rises abruptly from 
the shore in ranges of limestone cliffs alternating with steep 
slopes, covered with a dense wind-swept forest-growth. On the 
western side the surface is scored by watercourses which traverse 
the volcanic basis. The streams, on meeting the limestone ter- 
races, dip underground and pursue a subterranean course to the 
sea. This aspect is in marked contrast with the eastern. In- 
stead of the dense wind-swept growth, there are wide open spaces 
alternating with belts of luxuriant bush which cover in the water- 
channels. The open spaces are often dotted over with Screw- 
Pines (Pandanus odoratissimus) with their curious prop-like air- 
roots, and are generally covered with a coarse herbage. In the 
volcanic part the soil is often bare, and shows bright red, yellow, 
or brown from the decomposing rock. When it is covered the 
tracts of voleanic formation can be recognized by the plants 
which grow on them: Afelastoma denticulatum and some of the 
Ferns are, I believe, never found elsewhere. The great crowns 
of the Tree-Ferns are conspicuous features when looking down 
M2 
