3 86

Plate IV.Fig. 2.

Appendix II.

To illustrate this, let A E D G be 3

Lens, F the Focus of parallel Rays, f the

Place of an Object O B ; through the Point

F draw a Line to intersect the Object 19

the Point B, and falling upon the Lens in

the Point A. This Ray will be refracted

into A M, parallel to the Axis of the Lei 15

F C O ; from f draw the Line F A, which

by the Lens will be refracted to its refp eC "

live Focus V ; then will LV represent th?

Image of Part of the Object B f; let IVl

be an Eye-Glass by which that Image lS

to be viewed, which therefore must h e

placed at its focal Distance P V; from lt

draw P L, and parallel thereto drawM^’

then will the Angle M O P be the viss 3. 'll

Angle under which the Image LV ' vVl1

appear in the Eye at O.

We are now to show how this Im 3 £ cmay be viewed with more Distinctnessand under the fame Angle and Apertureas before ; and this is effected by subs 1 ''tuting two Glasses PI I and U S instead 0the single Glass M N ; for by this Me^n 5we shall make the fame Angle by twofractions which before was made by 0°^and that will produce the desired Ess e< ^!for let the Glass HI be placed at itsDistance IP from the Centre of theGlass M N, then will the Ray A H (vvhi°

befct e