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The nfual kinds of projedion for particular maps are the 

 ftereographic on the plane of the horizon, the conical, and the 

 circular. 



In the firfl:, which is founded on the rules of perfpedlive, 

 equal tradls of country are reprefented as very unequal, gradually 

 encreafing as they recede from the centre of the plane of 

 projedlion ; hence no common fcale can be applied to the map, 

 which is therefore totally unfit for menfuration. 



The conical projedtion is fo called, as it is produced by the 

 application of a cone to a fphere, according to certain rules. In 

 this the meridians are right lines on the cone, converging at its 

 vertex, and perpendicular to the parallels of the lat. which are 

 circles, defcribed from the vertex as their common centre : The 

 diftance between the meridians is corredt, only on the two pa- 

 rallels formed by the interfedions of the fphere and cone, be- 

 tween which they will approach too near, and every where elfe 

 recede too far from each other ; and hence the area of that part 

 of the map delineated on the portion of the cone which falls 

 within the fphere will be lefs than the truth, while without 

 thofe limits it will proportionably exceed it. This is an in- 

 genious and elegant projection, and as the conical area between 

 its extreme meridians and parallels is perfedlly equal to that por- 

 tion of the fphere it reprefents, if the limits of the country de- 

 lineated on it perfedlly coincided with thofe lines, it would ne- 

 ceflarily give the tiue area: But this never happens, and to 



fpeak 



