Lexicon Technicum: Or, An Universal English Dictionary Of Arts And Sciences, fol. -

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1. 2. In PlanoConcave Classes, when the Ray.
2. Fall Parallel to che Aris, che Virtuat Pocus iS de
3. stane from the Clals che Diamerer oF the Conca
4. vits.
5. 3. In Plano. Concare Clases ; A5 107: 193:
6. Sorhe Radius of the Concarity:
7. Toche Distance oF ehe Virtual FOEUS.
8. 4. In double Concares oF the Came Sphere, Pa
9. Fallel Rays hare cheir Virrual Focus ac che Dictance
10. oF che Radius of che Concarier.
11. Bur Whecher the Concariries be equal or une
12. qual, ehe Virruat Focus, er Point of Divergency
13. the Parallel Rays, is decermined by this Rule:
14. AS theSum. oF the Radii oF boch Concariries:
15. Isro rhe Radius ot cither Concavier: :
16. S0 is che double Radius of cother Concarity:
17. T0 che Distance oF che Virrual Focus.
18. 5. In Concave Clattes, il ihe Poine co which che
19. incident Ray Converges, be distant trom the Glass
20. Carcher than che Virtual Focus oF Parallel Ray
21. The Rule findins che Virtual Focus oE chis RaY,
22. this:
23. A5 the Diserence berween che Distance oF chi
24. Poine trom ihe Otals, and the Distance oF the Vir.
25. tual Locus From che Class:
26. Is ro rhe Distance oF rhe Vircual Foeus:
27. S0 he Distance oF chis POInE OF COnVersenCC
28. Fromthe Glass:
29. Fo che Distance oF che Virtual Foeus oF chis
30. Convergins Ray.
31. S. In Concave Classes, is che Poine r0 which
32. che Incidene Ray Converses, be nigher c0 che
33. Clals chan che Vircual Focus of Parallel R ays: Th
34. Rule co find where it crosses the Aris is tMIS.
35. ASthe Fxce(S OF the Virrual Focus morechanchii
36. Poine OF Conversenc):
37. Torhe Vircual Focus:
38. So che Distance oF ehis Point OF ConVergenC)
39. From the GlaIS:
40. Foihe Distance os che Poine Where chis Ra)
41. croresche Anis.
42. 7. Fotind che Focus oF a Meniscus GlasS; sec
43. under the Word Menisens.
44. Practicat Rules for findins the FOci of Cilasses.
45. For Convex Spherick Classes.
46. IFit be a Plano Convex Class, makce it resect che
47. Sun against a WVall; Wve Mall on the. Wall perceire
48. CD IOLIS OL LISHL:, one more brieht wichin ano
49. Wal eill rhe brisht LIMasC IS aE iS Imallest, che
50. Cla(S is then distant trom the W all abOnEThC FOULH
51. abouc hass ee Ldaus d he Conrerier curna
52. trom the Sun: And che sccond Dittance is about
53. half che Radius of c’ocher Convexies litewile
54. As the Sum ot the Hac et Borh Converirs:
55. Toche Radius ot cirher Convexity
56. Soisthe double Radius oF che other Conrexs,
57. Toche Distance OF chC FOCUS.
58. ThC Foci os Concares ave obcairid by Reslecti
59. On; FOr aS a Concave Mirror, Ox Speculum, burrS
60. ac the Distance oF abBBE halF the Radius OF Mhe
61. Concarier; (0 a Concave Glass, beine supposed, a
62. Restectine Speculum, MaII unite che Rays OF che
63. Sun ac che Distance ot abour halt ehe Radius ot
64. the Caritr.
65. MP. HallesSDoctrine oF che Foci oE Spherical
66. Classes oF aHI Porrs, expoled cither 10 Di
67. vergins, Conrergins, or Parallel Rays, is ad
68. Follos. Sec Appendix 10 Molyneuxs Diop
69. ricte.
70. PROPOSTTION
71. Zo find he Fccus os any Pareet es Rays Divereine
72. trom, or Convergins ro a siven Point in the Aris
73. os a Spherical Lens, and inclined therero under
74. the same Anele, ihe Rario of, the Sines in Refra
75. ction dme onu.
76. Cthe Cenret et che Sphiere, Whereot it 15 2
77. Oche Object or Poine in che Axis, 10 Or FCOMC
78. Wtrich che Rays do procced.
79. OP a sivel tas.
80. Lex che Rario oF Retraction be 25 r 20s: Make
81. CRIOC O aSSTOr, FOF che Immersion O( 2 R aY;
82. OF aSr tO sFor the Fmersion: (that is, 25 che Sines
83. I. FOr Clases oF Imall SphereS, (thac is, OF OFche Aneles in che Medium which c’e Rayenters
84. deep Converities) applr chem cocheend ol a Scale eo cheir correspondins Sines in the Medium out ot
85. ot Tnches and Decimal Parrs, and expole chem be-
86. Fore che Sun; and upon the Scale we all find che
87. brighe Intersection ot the Rars exactr measured
88. ont; or expolechem in the LTole oE a dark Cham
89. ber, and phere a WVhice P’aper receires the distinct
90. Representarion oE distant Objects. there is the FO-
91. cus oF chis Clals. Thisis an unirerlal and cerrain
92. Wvaz For all Converes.
93. Whichic comes.)
94. And lavins C R Crom C comards O, che Poine
95. Rs Mall BC che Canic Cor all che Rays ot e
96. PoincO.
97. Then deaw che Radius P C il necd be, conti-
98. nued, and wichche Cenere R, and Distance O P
99. Crcep a touch of an Arch incerlecting P C in C.
100. the Line QR being deawn, Mall BC Parallel coche
101. refracted Rar; and P F beins made parallel there.
102. For a Clato ot a prels sonB Locuo, erde co Mall incerseet che Axis in che Poine F, wohich is
103. fome distane Objects chro ic, and recede from the FOCUS TOUGHE.
104. he OlaIS, tillthe Fre perceires all in C’onfusion, Or
105. rill che Objects besinco axpeas inverced; liere Ese
106. Eye is in che Focus.
107. Or matie iE a5 CO: CP:: CR: CF, ane
108. CF Mall be the Distance os ehie Focus seom ihe
109. Demonstration.
110. FHCL MMOTC obscure, WIC a MC Cales Fromthe
111. Pa OF is Focal L. enBch.
112. TFic be a double Loc exPole each side r0 che
113. ces ofrheClals trom the all. LIC SI BManceis
114. Sun in like manner, and oblerre boch the liltan-
115. Whence che Locus is Found by chis Rule.
116. Thus we hare che Radii ot the rmo Conrexicies;
117. Let L Bethe Lens.
118. P any Pone n is Surtace.
119. Vile Polechereot.
120. Scoiment.
121. Ceriter ot the Sphere.

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Lexicon Technicum: Or, An Universal English Dictionary Of Arts And Sciences, fol. - . Machine transcription, not an edition: Leibniz Legible (model FoNDUE-GD_v2_ft_Leibniz, run 74). https://leibnizlegible.com/page/806933011:0346?run=74