( 207 ) 
Now we may conceive thefirfi: of thefe Portions, 
or Zones, to be converted from a fpherical Surface 
to a plane Surface in this manner, without fenfible 
Error. Let the middle Line of this Zone, that is 
the Equator, continue in its Situation, and let the 
Segments of the Meridians on each Side be con- 
ceived to unbend themfelves gradually, ’till they are 
extended into right Lines perpendicular to the Equa- 
tor : Then will that which was before a Zone, or 
Portion of a lpherical Surface, with a fmall Altera- 
tion become a Portion of a cylindrical Surface, cir- 
cumicribed about the Sphere ; whofe Breadth is 
every where equal to ten Degrees of the Sphere, and 
whole Circumference is equal to the Equator. And 
thus every Parallel to the Equator, as far as that of 
five Degrees of Latitude on each Side, will be 
ffretch’d and extended into a Circle as large as the 
Equator ; but they will all keep the fame Diftance 
from one another, and from the Equator, that they 
had before. This Extenfion, or Alteration, will be 
every where regular and uniform, and will be but 
very little, even where it is moft : For the lead of 
thefe Circles, which is the Parallel of five Degrees 
of Latitude, has the fame Proportion to the Circle 
it is ftretch’d to, or the Equator, as the Sine of 8 5* De- 
grees has to the Radius, or as 9961947 to 10000000 * 
which approaches very near to a Ratio of Equality. 
And now it will be eafily conceived, that without 
undergoing any other Alteration, or Diftortion, this 
Portion of a cylindrical Surface may be rectified, or 
extended into a plane Parallelogram, whofe Length 
will be equal to that of theEquator, and whofeBreadth 
will be equal to anArchof icDeg/ofthefameEquator. 
D d 2 And 
