x l v iii INTRODUCTION. 



Francisco did not occur until the 20th October. The solar radiation 

 17-7; greatest difference 32, least 2-5. 



The temperature of San Francisco is lower than in the interior of 

 California. In the valley of the Sacramento the thermometer often 

 rises to 114 in the shade; the valley is confined between two moun- 

 tain ranges, that bordering the coast, and the California!! mountains, 

 from 6000 to 9000 feet in height. The prevailing Avinds pass over 

 the valley nearly at right angles to it, on their course towards the 

 interior of the country, to fill the partial vacuum caused by the rare- 

 fied air over the vast arid and barren waste which occupies the centre 

 of California; their moisture being condensed on the mountain ranges, 

 they have none to impart to give fertility to the soil. 



PEACOCK'S CRUISE TO KINGSMILL GROUP. Plate XXIII., Ap- 

 pendix, exhibits three diagrams, one showing the track of the Pea- 

 cock from Oahu across the equator, to the Samoan Islands, in 15 

 south latitude, a distance of 2000 miles, thence to the Kingsmill 

 Group, and from the latter passing out of the tropics to the latitude 

 of 35 north, on her return to Oahu. On the other two is projected 

 the variations of temperature of the air and water, and the oscillation 

 of the barometer. It is almost needless to call attention to the re- 

 markable results exhibited by the latter, showing the depressions of 

 the barometer while within the basin of the Pacific, and how imme- 

 diately the pressure increases after passing beyond the parallel of the 

 tropics. The Peacock during this cruise passed within the area of 

 the ocean having the highest temperature on the surface of the globe, 

 which lies just to the north of the Samoan Islands. The climate of 

 the Kingsmill Group is divided into two seasons. During the stormy 

 season, from October till April, the northwest winds prevail ; but they 

 are occasionally visited by heavy southwest gales, which last several 

 days and resemble typhoons; they veer round to the north-by-west. 

 From April till September they have an uninterrupted succession of 

 fair weather, clear skies, with the wind constantly from the eastward. 

 During the month of April the mean temperature was 82 - 9; maxi- 

 mum 86, minimum 78, mean solar radiation 18 % 6, maximum sun 

 132, minimum 98. 



The climate as respects temperature is an equable one, and although 

 the temperature is high, it is not found to be oppressive, owing pro- 

 bably to the prevalence of breezes. The mean standing of the baro- 

 meter was 29 - 867 in., its oscillation -230. The rains are violent in 

 the stormy season, but in the fair, they have but occasional showers. 



