viii INTRODUCTION. 



of tin- (lulf Stream. It will be seen we pa-ed without the Gulf 

 Sir. .mi. in longitude about 60 west, yet we continued to be carried 

 <>n\\:inl by an easterly em-rent, until we reached the longitude of 

 45 wtt Tin- temperature <>f the water during this passage between 

 the latitudes of 32 and 42 N. was generally higher than that of the 

 air; the difference in temperature of the ocean on the two sides was 

 !v 7. although we had decrease" 1 our latitude 4, and this gra- 

 dualh from the Tinted States to Madeira. The mean temperature of 

 the water was 7i'.'S . and that of the air 7-Vl. which will express the 

 stan.liu.ir if the theniioineter in the Atlantic within these parallels 

 for the months of August and Septeml)er. 



The mean height of the barometer was 30-21 H, which is higher than 

 it ranged at any other time during the voyage. Kasterly winds were 

 found to have a tendency to elevate the column, while those from 

 the western quarter depres-ed it. The mean degree of moisture on 

 this passage was '666. 



MADEIRA Whilst at Madeira, the mean standing of the barometer 

 wa- .",11-171; in.; mean temp, of the air 71''.l r ; water 7.'!'G C . We found 

 the height of the vapour plain to be about 4.0lt(l feet above the level 

 f the sea, which, according to mir measurements, corresponds with 

 that of the height iif the Koehe d'Kni|>efia. observed to be the highest 

 jMiint (if cultivation. There is little doubt that the vapour plain must 

 have considerable inlluenee upon the climate of Madeira as well as 

 it- priidiietinns. In determining the altitudes of this island, an oppor- 

 tunity was afl'iirdcd us of ascertaining the decrease of temperatun> as to 

 elevation : the result of simultaneous observations gave for the altitude 

 uf I'ieo Iluivo (fl,180 feet), 254 '1 feet for each degree of temperature, 

 that ..f IJorhed'Kmpena ( I. lull feet), 3S4-li feet, and that of Camancha 

 '"I feet), 333 feet. The observations \\eiv made between meri- 

 dian and 1'. M. 



The degree < if nn list ure at Madeira was --V-iH. 



MADEIRA TO RIO JANEIRO This |. nccilpied a period "f 



til'tv-nine da\ .-. in.-ludin- t\\i. <la\ s' delay at 1'ortn l'ra\a. Bet\\een 

 ira and I'm to l'ra\a i Is of latitude), the water and air incriM- .1 

 in temperature '.'' . the fnrmer liein- -enerall\ t\\o <le-ive> warmer. 

 The tr.id-- wind- weiv met with in the latitude of 'J7' north; previous 

 to whii-h we experience | a -tron- liive/e. whose limit included some 

 of the vessels of tin- ><|uadron. earr_\ ing them rapidly onward, while 

 the nthei- wen- l,.ft for -e\,-ral hours U-ealmed. These winds are 

 it mo-t frei|iieiit oeeurrence at the outer \erge of the trade winds. 

 and partieiilarly on the eastern side of the Atlantic: though no doubt 



