xii INTRODUCTION 



ami eastward, ami from A|ril to September from the southward and 

 eastward. These winds apjH-ar to exorcise much influence on the cli- 

 mate- of Brax.il. 



BIO DB JAHEIBO. Our observations at Rio were continued through 

 a period of fort \-four days. The highest range of temperature we ex- 

 perienced was 93 Fahr., and the lowest 68 the mean being 77'5. 

 Tli.- mraii 1. a ro meter, ml uc < I to :;:T Fahr.. 29'899 inches; the oscilla- 

 tion .if the- im-reurial column was '710 in. The tropical hours were 

 for tin- minimum at 3 A. M. and 3 p. M. ; the maximum appears to have 

 IN, -n deferred until between the hours of 10 and 11 A.M. and P.M. 

 The degree of moisture -796. Tin- mean temperature of sun's rays 83, 

 the maximum In-ing 117, while the minimum was but 70. The mean 

 annual temperature, as determined by the thermometer placed in a 

 well twelve feet Mow the surface, on the island of Enxados, \\as 

 76-98* Kahr. The mean annual temperature, as determined by J. 

 Gardner, Esq., which he obligingly furnished me. the day observa- 

 tions for nine years, was 77'01; the highest range of tin- thermometer 

 was 93, in the month of February, and the lowest 64. in tin- months 

 of.liilv and August. From these data Rio Janeiro does not appear 

 to possess a warm i -Innate, yet it seems so to the feelings; the heat 

 during the morning hours, between the times of the land and the sea 

 breezes, is ex-----i\e. The range of the photometer while at Rio was 

 between 5 and 100. The climate is a very equable one, as will 

 appear by t lie mean monthly temperature lor six years, represented 

 on the diagram. Plate 111., page 74. 



The rains o<-eiir in every month in the year, and there is very little 

 difference in the number of rainy days; the greatest quantity, how- 

 ever, appears to fall during the month.- of heeeml>er. January. Feb- 

 ruary, and March. There has been no measurement of the annual 

 quantity of rain, that I am aware of. During the summer months 

 tin- rain usually falls in thunder-gusts, which arise in the south\\--.-t ; 

 these occur in the afternoon, between the hours of four and six, are 

 very \io|i-nt. the rain falling in torrent-. The wind at Hio generally 

 alternate- b.-t\\eeii the land and sea lnve/es. which l>oth tend to 

 diminish tin- heat of the climate. On the coast of llra/il. the tropical 

 or northeast- -rly monsoon blown during the Mimmer mouths. \i/... from 

 Ix-r to March, and the southeasterly monsoons during those of the 

 winter. These may IN- .-aid to cause the vicissitudes of the climate. 

 DuriiiL' the latter season, gales of wind prevail from the south. \Ve 

 cannot fail to r- mark, on iiis|n-eting the diagrams on Plate 111., page 74, 



