XIX THE PHYSICAL CONDITIONS 211 



The great daily range of temperature is one of the most 

 striking features of the climate of the summit of Mauna Loa. The 

 extreme recorded by me was 387°, whilst Wilkes registered as 

 much as 42°. As on most lofty mountains the dryness of the air, 

 as indicated by the relative humJdity, was usually great. The 

 average percentage during my stay between 8 and 9 A.M. was 

 44, at midday 43, and between 5 and 6 P.M. 56. This may be 

 contrasted with 72, the average for the year at Honolulu. In the 

 tropics the mean for the year in the lower levels often rises to 80 

 and over ; and it can scarcely be doubted that the Hawaiian 

 climate is generally drier than it was before the destruction of the 

 forests. The lowest relative humidity recorded by me on the 

 summit of Mauna Loa was 20 per cent. Junghuhn on the summits 

 of two mountains in Java, 10,500 and 1 1,500 feet in height, recorded 

 percentages as low as 5 and 13. Further details relating to this 

 subject are given in Note 61. The rainfall on the top of Mauna 

 Loa is probably very slight. During my sojourn rain was noted 

 on six days, but on only two could it be measured, and the total 

 fall could not have amounted to over a third of an inch. 



The mean annual temperature of the great forest-zone at the 

 elevations where it displays the greatest luxuriance of growth 

 on the island of Hawaii, that is, between 4,000 and 6,000 feet, 

 would be estimated at 63'' and 57° R, if we take the rate of 

 decrease before employed of about three degrees per 1,000 feet. 

 But remembering the heavy rainfall in this region and the usual 

 occurrence of a protecting belt of cloud during the day, this might 

 seem to be too high. According, however, to a table given by Mr. 

 Jared G. Smith in his annual report of the Hawaii Agricultural 

 Experiment Station for 1902, the average temperature at 4,000 

 feet would be 65°. I cannot help thinking this is excessive as an 

 average for the island. In the latter part of May, 1897, the mean 

 temperature during my sojourn of twelve days at elevations between 

 6,000 and 6,700 feet around the slopes of Mauna Kea was 51*2° ; 

 whilst for eight days in the first part of June in the same region 

 the mean temperature was 58"2° at an altitude of 4,000 to 4,300 



feet. 



It is possible, as I have pointed out on a later page, to recognise 

 in the different zones of vegetation the floras of a variety of lati- 

 tudes ; and these zones are to a large extent controlled by temper- 

 ature as well as by other conditions. Thus the Fijian would be 

 amongst familiar vegetation on the lower slopes of Mauna Kea, 

 whilst the Maori would be at home halfway up the mountain- 



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