EQUATORIAL TEMPERATURE. 



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change of climate or physical conditions, such as 

 characterise the tropical and temperate zones in their 

 full development. There will be a gradual transition 

 from one to the other, and in order to study them sepa- 

 rately and contrast their special features we must only 

 take into account the portion of each in which these are 

 most fully exhibited. For the temperate zone we may 

 take all countries situated between 35° and 60° of lati- 

 tude, which in Europe will include every place between 

 Christiana and Algiers, the districts further south form- 

 ing a transitional belt in which temperate and tropical 

 features are combined. In order to study the special 

 features of tropical nature, on the other hand, it will be 

 advisable to confine our attention mainly to that portion 

 of the globe which extends for about twelve degrees on 

 each side of the equator, in which all the chief tropical 

 phenomena dependent on astronomical causes are most 

 fully manifested, and which we may distinguish as the 

 equatorial zone." In the debateable ground between 

 these two well contrasted belts local causes have a pre- 

 ponderating influence ; and it would not be difiicult to 

 point out localities within the temperate zone of our 

 maps, which exhibit all the chief characteristics of 

 tropical nature to a greater degree than other localities 

 which are, as regards geographical position, tropical. 



Temperature of the Equatorial Zone. — The most 

 characteristic, as it is the most important feature in 

 the physical conditions of the great equatorial zone is 

 the wonderful uniformity of its temperature, alike 

 throughout the changes of day and night, and from one 

 part of the year to another. As a general rule, the 

 greatest heat of the day does not exceed 90° or 91° 



B 2 



