PHYSIOGRAPHY. 



[chap. 



outline of the country be projected on this cone; then, 

 on unfolding the paper, it may be spread out on a flat 

 surface : hence this method is known as that of conical 

 development (Fig. io8). Most maps of Europe furnish 

 examples of this construction. 



Any of these maps will serve tolerably well for the use of 

 landsmen, but they are not what the mariner wants. He 

 requires a chart which will give him the true bearing of 

 places, so that he may steer direct from one point to 

 another, and this he gets by the use oi Mercator' s projection} 



Fig. io3. — Conical dsvelopajeat. 



Suppose the outlines of the various countries of the world, 



and the system of lines of latitude and longitude, were 



depicted on a globular bladder placed inside a glass cylinder ; 



on blowing more air into the bladder it will stretch in all 



directions, and it may be supposed to be sufficiently elastic to 



press on all sides against the inner surface of the cylinder. 



The parallels of latitude then touch the glass, and form circles 



round the cylinder, while the meridians stretch out, and 



1 Mercator was a native of Flanders, born in 15 12. His real name 

 was Gerald Kauffman, but, according to the custom of the times, his 

 surname, which means a merchant, was translated into Latin as Mercator. 



