INTRODUCTION. 



On the mountain, it was frequently impossible to obtain the dew 

 point with either of the hygrometers of Daniel or Pouillet ; the eva- 

 poration was very small and slow ; the snow continued almost un- 

 changed, even in strong sunshine. The vapour plain, or the height 

 at which the clouds usually remained, was about 5000 feet above the 

 sea; the horizon above this was ill denned, the sea and sky being 

 blended together by a blue haze ; within the regions of clouds echoes 

 were rife. During the whole period of our stay, we saw nothing 

 of the blackness of the heavens which is spoken of by travellers; 

 on the contrary, it appeared to us of a beautiful blue. One of the 

 most sticking of the phenomena was the shadow of the mountain 

 thrown on the eastern sky, as an immense dome, of a light amethyst 

 tint on its outline, and gradually deepening to a dark purple towards 

 the centre. 



When above the vapour plain, electricity was readily developed ; 

 at times the feeling was that of being insulated and charged from 

 an electrical machine; the gold-leaf electrometer showed but little 

 change, except on two occasions, when it appeared greatly excited. 



The quantity of snow which fell while we were at the summit of 

 the mountain, was about 18 inches; at the recruiting station, altitude 

 9000 feet, there was rain. The wind, for the most of our stay, was 

 from the southwest, while it was blowing from the north and north- 

 east at Hilo. The greatest velocity of the clouds during the south- 

 west gales was found to be 47 miles an hour. All the gales which 

 we experienced (seven in number), occurred at night, being most vio- 

 lent between the hours of 11 p. M. and 4 A. M., and but one of these 

 was felt at Honolulu, while at Hilo they did not experience any gale. 

 The clouds were seldom seen above the height of 8000 feet, except 

 during the stormy weather. The temperature of the sea around the 

 islands is 79'5. 



HAWAIIAN ISLANDS TO COLUMBIA EivER. Our route to and from 

 the Northwest Coast, is projected on diagram, Plate XVI., page 516. 

 Both passages were made in the usual track which sailing vessels are 

 compelled to take. Twenty-one days in April were occupied in the 

 first, and twelve days in November in the latter. After leaving the 

 Hawaiian Islands we lost the northeast trades in 24 north latitude ; 

 calms, with light variable winds succeeded until the 28th parallel of 

 latitude, when we had southeast and northeast winds, and finally as we 

 approached the coast, they came from west and northwest. The tem- 

 perature of the air and water continued to fall rapidly, equal to 1 for 



