PHYSIOGRAPHY. 



[chap. 



distance, and to depict what he sees upon a flat plane 

 which is placed between his eye and the earth^ (Fig- io6). 

 But his representation will be distorted much in the same 

 way as the shadows of objects are distorted when the 

 light does not fall square upon their surfaces. Hold a 

 plate in the sunshine, in front of a flat surface, and, when 

 the light comes down perpendicularly upon it, the shadow is 

 a true circle ; but, incline the plate, and the circle passes 

 into an elhpse ; and, as the plate is inclined more and more, 

 so the ellipse gets narrower and narrower, until at last, when 



F^iG. 106. — Orthographic projection. 



Fig. 107. — Globular projectiori. 



the sunlight is passing along the edge of the plate, the 

 shadow is reduced to a straight line. The shadow is said 

 to be projected on to the flat surface ; and the method of 

 throwing a representation of the rounded surface of the 

 earth on to a flat sheet of paper is also called projection. 



In the method of projection which has been just ex- 

 plained — that in which the eye of the map-maker is supposed 

 to be infinitely distant — the central parts of the hemisphere 



' This is tlie method of orthographic projection. 

 latitude become straight lines, as seen in the figure. 



The parallels of 



