liv 



INTRODUCTION. 



with some of the islands in the Pacific similarly situated. The 

 first phenomenon differing from the islands situated in the saint- 

 latitude in the Pacific is the constancy of the southeast trades; 

 these blow almost without intermission throughout the year, be- 

 tween the southward and eastward. There is no change during the 

 summer months, either in the cessation or fluctuation of the trade 

 winds, excepting for a few days in June, when they blow from the 

 northeast. Its temperature is much lower, corresponding with the 

 surrounding ocean. The variations throughout the year at Jamestown 

 do not exceed 13, from 66 to 79 and the oscillation of the baro- 

 meter -065. The height of the vapour plain is about 2,000 feet. 

 Rain falls in frequent showers; the annual amount, in 1842, accord- 

 ing to observations made at the observatory, 1765 feet above the 

 ocean, was 79 - 40 inches; but this would not be obtained elsewhere on 

 the island, it being on that part fully exposed to the southeast winds, 

 and where the deposition is going 011 almost constantly, a position 

 that can hardly furnish a fair criterion of the climate of this sea-girt 

 island. 



We carried the southeast trades to 1 south latitude, in 3Q west 

 longitude, and the same day entered the northeast trades, which 

 continued uninterrupted, and freshened as we advanced to the north- 

 ward and westward, until we reached the parallel of 25 north. 

 in longitude 61 west, where we lost them. As we approacht'd the 

 vicinity of the Gulf Stream, we had the wind from the southward and 

 westward, and variable. We crossed it, with strong winds from the 

 eastward, in latitude 35 20' north, and 73 45' west longitude, where 

 we found it forty-seven miles in width; the highest temperature was 

 found on its inner edge, the thermometer standing at 79 Fahrenheit, 

 and but a short distance within 67. In this passage the variation of 

 the temperature of the air and water together, with the oscillation of 

 the barometer, were similar to what we found them on our outward 

 voyage. The diagram on Plate XXII., page 726, exhibits the result. 

 The highest temperature occurred in and near the equator, in longi- 

 tude 30 west. The barometer, it will be seen, continued depressed 

 below 30 inches, between 15 south and 15 north latitude, our track 

 passing over the equatorial Atlantic in a northwest ilire.-tion. 



THE CRUISES OF THE PORPOISE AHD BELIEF The diagram on 



Plate XXIV., Appendix, shows the results of the observations made 

 with the synipiesometer and barometer on hoard the Porpoise and 

 It.-lief when detached on separate service. It will be seen that these 



