INTRODUCTION. XXxix 



ation is about 12 Fahrenheit, and its extreme annual range 37. The 

 solar radiation 21'4. The climate of these islands varies according to 

 the elevation; in speaking of the climate, I allude to that part on the 

 coast, nearly on the sea level. The moisture depends upon the situation, 

 whether high or low, or on the leeward or windward sides of the island; 

 the leeward side is free from rain, while the windward side has an 

 almost constant succession of showers ; these continue during the preva- 

 lence of the northeast trade winds, which last for nine months of the 

 year, from March till December. In the winter months they are sub- 

 ject to calms, and occasionally to southwest gales; these do not appear 

 to partake of the whirlwind character, but are accompanied by a 

 deluge of rain. 



The trade winds blow with great strength during a part of the day, 

 but the nights are calm and beautiful. In the summer months heavy 

 dews prevail, but they are not considered unhealthful. The inhabi- 

 tants generally prefer to reside on the leeward side of the islands. 

 The quantity of rain which falls annually is variable; at Honolulu, 

 in 1837, it was 21 - 1 in., and in 1838, 46 - 8 inches. 



During our stay at the island of Hawaii, we ascended to the top of 

 Mauna Loa, 13,4-40 feet above the level of the sea, and 60 miles west 

 of Hilo. In order to give some idea of the position which we occupied, 

 and where the phenomena were observed, the following description of 

 the shape of the island of Hawaii seems necessary. It is of triangular 

 form, with its longest side to the west, and embraces about 3500 square 

 miles ; its whole surface is occupied by three mountains. Mauna Loa 

 is nearly in the centre, and is a huge flattened dome, rising from a 

 base 60 miles in diameter; Mauna Kea, 27 miles to the north, 14,000 

 feet elevation, and to the west; Mauna Hualalai, at a distance of 24 

 miles, 10,000 feet high. Between the three mountains lies a vast 

 plain, strewed with lava and ashes, which the mountains have vomited 

 forth. All the surface above an elevation of 6,000 feet, is destitute of 

 wood. The top of Mauna Loa has a crater one mile in diameter, 

 and 760 feet deep : our position was within 80 feet of the edge. The 

 simultaneous observations were continued through a period of 9 days ; 

 they are projected on the diagram, Plate XV., page 490. The oscilla- 

 tions of the barometric column, it will be seen, are nearly coincident, 

 but in the thermometers we find that the range is much greater at the 

 summit than below, and that even the maximum and minimum hours 



was placed in a bottle of water, which was buried in black scoriae, and remained there 

 fifteen days. 



