5 ?

Optics.

Structure of these Microscopes may benc * in my Micrographia Nova , together

with

^ le ^irrour A D, is to the fame seen from the Ver-

v of the Mirrour a d as vp to V s, or asr, \ T vp

of ^ a .;^y» the Image OP seen from the Vertex ve speculum a d, is to the fame seen through the

y e ~Glass G, as G P to P v, or as -^-g. Where the

VTX

^ magnifying Power is as A X ~ X Jflfl to I.

a8 ^mrivanec we owe to Dr. Smith of Cambridge.stru^'j “ ut a better .Form and easier Method of con-Mi r ® a Catoptric Microscope, with two reflectingCafJ^ 2 ^’ that which follows. ABCDEF is aCa Ve (? r Tube, in one End of which is placed a con-the p P ecu lutn G H, with a Hole I K in the Middle;s 0 ent re of this Speculum is at c, and its Focus at O,plac^ ^ O — Oc. At the open End of theTube is

lar ;r Wsll s^ >t is moveable nearer to or farther from the

oy^. a ^fniall convex Speculum d e f, on a Foot e f,

■sgej. O

2 ‘rP^ulum, GH, as Occasion requires,of Y now sn Object a b be posited in the Centre cfo t>icd ar g e Speculum, the Image thereof a b will beati(] m the lame Place, as has been shewn already;

a Mi

5 Consideration is all the Reason of this Form of

as ari (si 'sope ; for, if now we look upon the Image absocij s . nearer to the convex Speculum d f than its

therefi t * S P^dn a larger Image AB will be formed

Cee din^ V' ^he Foeus <7 ; or tbat Rays cQ, cH, pro-teflefA Y° m ail y Point c in the Object ab, will becul ar hack upon themselves, as being perpendi-tvi th o the Speculum ; but the refracted'Rays meeting°n, the convex Surface of the Spe-the p *> will (as they tend to a Point r, nearer thani ° CUs f) be reflected to a Focus C, which is found

y the Theorem (Jnnot. CXXV).rfl-id J

E 2

3°'

For

PlateXL VII.Fig. io.