280 



CONCLUSION. 



with ours, and where it is equivalent and repre- 

 sentative. Lastly, in an easterly direction it has 

 to extend to the region of the Caspian and Aral 

 Seas. 



The map here given is on what is called the 

 " globular projection," and its advantages are, that 

 equal spaces on the sphere are represented by equal 

 spaces on the plane ; relative dimensions are pre- 

 served ; but as the rectangular spaces on the sphere 

 are not represented by like spaces, the forms of 

 countries are somewhat distorted. It will be seen 

 that this defect exists to its greatest extent towards 

 the circumference east and west, as in the North 

 Pacific and in the Bay of Bengal ; but that for the 

 central portion — that with which we are here more 

 immediately concerned — the meridians and parallels 

 of latitude do not depart much from right-angles. 

 In this map, which is a perspective view of the 

 northern hemisphere, the sphere is represented as 

 it would be seen on the horizon of London at a 

 distance of sixty-eight hundredths of the radius 

 from the surface. 



Oceans, seas, lakes, and rivers, mark what are 

 now the depressed portions of the earth's surface ; 

 physical arrangements, however, have not always 

 been such as they now are ; the past history of the 

 globe presents an almost endless series of changes 

 in the relations of land to water : and as the natural 

 history of our existing seas may enable us to read off 

 the bathymetrical conditions of older sea-beds, so 



