312 PHYSICAL GEOGRAPHY. [1840 



islands are divided in the same manner by deep sea channels, 

 of greater or less width, in which vessels are often protected, 

 in a degree, from the violence of the waves in the open ocean, 

 by the immense coral reefs that encircle the group. These 

 are low and sunken in many places, and unless provided with 

 a correct chart, or the weather be particularly favorable, it 

 is dangerous for a strange vessel to attempt to pass through 

 the openings. Passages of this kind, however, are quite 

 numerous, and once inside the reefs, still water ma^ fre- 

 quently be found, even when the storm rages the most fear- 

 fully without. 



(2.) Quite a variety of scenery is presented in this group 

 of islands. Eooa is rocky and barren, and rises to the height 

 of six hundred feet above the level of the sea. Tofooa, one 

 of the smaller islands, attains a still greater elevation, and is 

 the highest of the group. Hapa'i, Vavao, and Tonga, are 

 much lower, and far more fertile. Some of them are of volcanic 

 origin, and exhibit all the distinctive features peculiar to that 

 formation ; but the only active volcano is on the island of 

 Tofooa. Others are the work of the coral. Tonsra is low 

 and almost level ; there being only here and there a small 

 hillock from twenty to forty feet high, and near the northern 

 extremity of the island a conical hill about sixty feet in 

 height. It is not far from one hundred miles in circumfer- 

 ence, and has a shallow lagoon, like those in the atolls of the 

 Paumotu Group, extending some ten miles into the interior, 

 though, of course, surrounded by a much greater mass of 

 elevated ground. 



Hurricanes and earthquakes are frequent, and the former 

 are very destructive. Rain falls in great quantities, and 

 heavy dews descend at night. The mean temperature in the 

 summer months is about 80°, and the thermometer often rises 

 to 98° in the shade. In consequence of the moist atmosphere, 

 the oppressive heat, and the sudden transitions from the ex- 

 tremes of temperature, the climate is not at all healthy, 

 though the natives, where their habits are regular, frequently 

 live to an advanced age. Fevers, with the exception of in- 



