3 o 8

Plate

LXVIIL

F ‘g- I.

The Use of the Globes.

of the Disk than on the Outside, and why then' n^eis always unequal; with other Phsenomena of cNature. ^

7. The Stereograpbic Projection ot 0 $

SThere is that on which our Maps are c 0 in, 1 si> emade, and depends on this Principle, That i-f ^5 a-jolhof any Meridian be supposed the Plane of the P r °J e .j ^0-then an Eye placed in one Pole of that Meridian '‘V sit'ject all the Circles in the opposite Hemisphere n'cular Arches on the said Plane. Thus let AGDr £0 (MMeridian ; then the Diameter A D, dividing h ofupper and nearer Hemisphere, is called the a>AMeasures ; and an Eye placed at the Pole E wst*.Pevery Point B, L, G, in the opposite Semicircle it 1 foePoints H, I, C, into the Line of Measures A 'Visual Rays E B, E F, E G. tTsC cSi

8. Hence if the Arch A B ~ F G — to ffjfsstfPthen will their Representatives in the Line of * rfae A H and I C ; and the Points H and Ithrough which the Circles of

fP

ar e of ,

10 Degrees aP< Q 0 &

Degrees do pals in Projection, viz. the Circle*and GT E, as is evident from considering the.

Hence the Reason why the Meridians, do all 1 ^ ^ ot 1to each other in the middle Parts of the Map £ , p a ft s

the Outildes; and consequently, why the l' eveI f 1 jy[ap Srof the Earth cannot be duly represented on suchcither in respect of Magnitude or Position. . < si-"9. On E as a Centre describe the Arch C 1draw the Line E K ; the Arch G K will be p l °s^ cinto the Line C L, which is the Tangent of tbff ,r MCEL. But the Angle CEL is equal to P* 3 . Qb-Angle G C K, or Arch G K ; therefore any i VX n gr | 'jis projected into a Line C L equal to the^ j

„ , equal _

of Half that Arch. Hence the Line C D

ca 1

dra 1

. ^

the Live of Half-Tangents in respect of the OP

G K D. jvL3p S

10. On this Projection are. usually made all. t ^ (faesof the World in two Hemispheres; there is a fu e M e 'calPd the Globular Projection, wherein all Qj 0 \jCridians are equally distant, as they arc; on the ^itself. They are circular Arches here, as in the a

jection, and are drawn after the same-Mann^r*

1

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