INTRODUCTION. XXXVli 



creating a greater pressure of the atmosphere. I have before remarked 

 that the climate on the east and west sides of the large islands is dif- 

 ferent; a fact we had an opportunity of proving while engaged in this 

 Group. At the same hours we found the mean difference of the tem- 

 perature to be 2 less on the lee side than it was on the weather 

 side, but the greatest difference was 4-23. This was doubtless 

 the effect of condensation taking place on the weather side, while 

 evaporation was going on rapidly on the lee side. The standing 

 of the barometer was also found to be '126 in. higher on the wea- 

 ther side. The diagrams on Plate XIII., page 402, exhibit the 

 mean daily variation of the thermometer and barometer, that at 

 Ovolau while we were stationary, and the other while we were 

 moving about from port to port of the northern large island. The 

 variation of the temperature may be attributed to the advance of the 

 season rather than to any change of locality. During our stay, the 

 lowest temperature shown was 68, and this in mid-winter. Feb- 

 ruary and March are considered the 'most stormy months, when heavy 

 gales are frequent. Those that have been experienced, begin at the 

 northeast and shift round to the north and northwest, from which 

 latter quarter they blow with most violence, and clear off with the 

 wind from the west and southwest. 



I endeavoured to trace the gale which happened at these islands 

 on the 22d and 23d February, in some connexion with those which 

 occurred at New Zealand, but without success. Strong winds pre- 

 vailed at Tonga, but they had no gale there. The same gale, how- 

 ever, was experienced off Erromango; the time of its occurrence being 

 the 28th, 20th, and 1st March; the position was between 500 and 600 

 miles to the west-by-south of the Feejee Group. The wind was from 

 the southeast to south-southeast; this would lead to the belief that 

 the storm had passed to the northward and westward, travelling to 

 the westward. 



The mean solar radiation at the Feejee Group was found to be, sun 

 97, shade, 72, difference, 25; maximum, 110, minimum 82. 



FEEJEE GROUP TO HAWAIIAN ISLANDS. In this passage we made 

 a course about north-northeast, from 17 south to 21 north latitude, 

 traversing the central part of the Pacific, on a line 2500 miles in extent. 

 On Plate XIII., page 402, the track is shown, and the variations of the 

 instruments. The depression which took place in the barometer, 

 cannot fail to be remarked on inspecting this diagram ; and in order 

 to show that this was not only the case on one passage, I have given 



10 



