( 2°4 ) 
Xf. The Conftru&ion and Ufe of Spherical 
Maps, or fnch as are delineated upon Tortious 
of a Spherical Surface. (By Mr. John Col- 
fon, M. A. F. % S. 
Eographical Maps, and Hydrographical Charts, 
J though they*are Reprefentations of a Convex 
Spherical Surface, yet were firft delineated upon 
Planes, as being the mod eafy and obvious, tho’ 
not the mod natural and accurate Reprefentations : 
And they will be diffidently near the Truth, when 
the Part of the Earth or Seas to be defcribed is not 
of a very large Extent. Such as thefe have been 
ufuaily called Chorographical and Topographical 
Maps j but when the Map is any thing general, or 
is to contain any large Tradt of the Earth or Seas, 
fuppofe (for Inftance) one of the four Quarters of 
the World, as they are call’d ; then, when they 
are projected, or reprefented npon a Plane, the Parts 
muft neceffarily be diftorted, one way contracted 
beyond the Truth, another way dilated, fo as to 
give no juft Idea of the whole. Nor can this Di- 
stortion be poffibly avoided, when any confidcrable 
Part of a Spherical Surface, by any Projection what- 
ever, is to be reprefented upon a Plane. ’Tis true, 
this Diftortion is always regular, and according to 
certain Laws j fo that knowing the Nature of the 
Projection, it may tolerably well be allow’d for. 
But to do this fcientifically, and as it onght to be 
done, requires much Skill and Accuracy in the 
Maker, 
