ON ITS EXTERIOR. VOLCANOES. 377 



a terminal crater, but only hills of long extinguished 

 scoriae. Mouna Hualalai* is about 10,000 feet high, and 

 is still burning. In 1801 an eruption took place in 

 which the lava reached the sea on the western side. 

 It is to the elevation from the bottom of the sea of 

 the three great mountains of Loa, Kea, and Hualalai, 

 that the whole of the island of Hawaii owes its origin. 

 In the descriptions of the many ascents of Mouna Loa, 

 among which that given by Captain Wilkes' Expedition 

 rests on examinations continued during 28 days, a 

 fall of snow with a temperature of from 9 to 14 

 below the freezing point is spoken of, and single patches 

 of snow near the summit are said to have been seen 

 from a distance by the aid of a telescope ; but perpetual 

 snow is never mentioned. ( 5l4 ) I have already remarked 

 that according to the measurements which we may now 

 regard as most accurate, 13,759 feet for Mouna Loa, and 

 13,951 feet for Mouna Kea, those mountains are fully 

 1000 and 800 feet below what I found to be the lower 

 limits of perpetual snow on the continental mountains of 

 Mexico in 19^ of latitude. We should expect to find 

 the limit of perpetual snow rather lower down on a small 

 island than on a continent, on account of the influence of 

 the surrounding ocean in occasioning, in the hot season, 

 a lower temperature of the inferior atmospheric strata, 

 and the presence of a greater quantity of aqueous 

 vapour in the higher portions of the atmosphere over 

 the island. 



The volcanoes of Tafoa * and Amargura *, in the 

 Tonga group, are both active, and the latter sent forth 

 a considerable flow of lava on the 9th of July 1847. ( 515 ) 

 It is an exceedingly remarkable circumstance, and in 



