x ji INTRODUCTION. 



and eastward, and from April to September from the southward and 

 eastward. These winds appear to exercise much influence on the cli- 

 mate of Brazil. 



EIO DE JANEIBO Our observations at Rio were continued through 

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

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

 The mean barometer, reduced to 32 Fahr., 29-899 inches; the oscilla- 

 tion of the mercurial column was '710 in. The tropical hours were 

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

 been deferred until between the hours of 10 and 11 A. M. and P. M. 

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

 the maximum being 117, while the minimum was but 70. The mean 

 annual temperature, as determined by the thermometer placed in a 

 well twelve feet below the surface, on the island of Enxados, was 

 75'98 Fahr. 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 the thermometer 

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

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

 to possess a warm climate, yet it seems so to the feelings; the heat 

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

 breezes, is excessive. The range of the photometer while at Rio was 

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

 appear by the mean monthly temperature for six years, represented 

 on the diagram, Plate III., page 74. 



The rains occur 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 months of December, 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 

 the rain usually falls in thunder-gusts, which arise in the southwest ; 

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

 very violent, the rain falling in torrents. The wind at Rio generally 

 alternates between the land and sea breezes, which both tend to 

 diminish the heat of the climate. On the coast of Brazil, the tropical 

 or northeasterly monsoon blows during the summer months, viz., from 

 October to March, and the southeasterly monsoons during those of the 

 winter. These may be said to cause the vicissitudes of the climate. 

 During the latter season, gales of wind prevail from the south. We 

 cannot fail to remark, on inspecting the diagrams on Plate III., page 74, 



