PHYSIOGRAPHY. 



(Ill) DISTANCES AND AREAS ON MERCATOR'S AND GALLE'S 

 PROJECTIONS. 



On Mercator's projection 1' of Longitude is everywhere 8086 feet, 

 and on Galle's projection 1' of Longitude is everywhere 4311 feet, 

 In each case the Latitude is altered in proportion to the change in 

 the Longitude. The areas are the number of millions of square feet 

 in a quadrilateral the sides of which cover 1' of Longitude by 1' of 

 Latitude. Ratio of area on the map to the true area." 



(112) DIMENSIONS OF THE EARTH (cf. 9). 



If the earth be considered as an ellipsoid, the longer equatorial 

 diameter (2a) passes through the meridian 15 34' E., and the 

 shorter equatorial diameter (26) passes through the meridian 105 

 34' E. 



Longer equatorial semi-diameter (a) 

 Shorter equatorial semi-diameter (b) 

 Polar semi-diameter (c) 



20926350ft. 

 20919972ft. 

 20853429ft. 



6 378 294 m. 

 6 376 350-4 m. 

 6 356 068 -1m. 



