48 INFLUENCE OF OCEAN CURRENTS. 



shows, the coasts of Labrador are bathed by an icy 

 stream, known as "The Hudson Bay Current,"* de- 

 scending from the arctic regions. These extensive 

 streams of warm and cold water, respectively, either 

 raise or lower the temperature of the air in their 

 vicinity, and thus produce great variations of climate 

 between these countries situated within nearly the same 

 parallels of latitude, which under the circumstances is 

 not much to be wondered at. 



So again in almost every instance, where sharp curves 

 of the isotherms warn us of marked abnormal increase 

 or diminution in the temperature of a particular region, 

 local causes are apparent, which furnish very good 

 reasons why such peculiarities should occur. It would, 

 however, be out of place to enter into details respecting 

 these phenomena in a preliminary and explanatory 

 chapter upon the Climatic Zones generally; and we 

 shall close these remarks by giving a table in which 

 the name and locality of each of them is clearly indicated, 

 which will give our readers a general idea of our system. 



The Climatic Zones, which girdle the earth, both 

 by land and sea, are six in number; and occur in 

 corresponding positions in both hemispheres : there are 

 therefore two examples of each ; one to the north, and 

 the other to the south of the equator. 



We have ventured to fix their position and boundaries 

 (beginning from the equator), respectively, as follows: 



i. THE GREAT FOREST REGION OF THE EQUA- 

 TORIAL ZONE. 



* See, The Royal Atlas of Modern Geography by Alexander 

 Keith Johnson, Map 2, Chart of the World on Mercator's Projection 

 Showing the Direction of the Ocean Currents. 



