IKDKX. 
203 
Micrometer ocular, coordinate. I.'". \ ''>': 171. 17.'.; Planes, equivalent. l', nla!. Is; principal. 18. 
103; double -crew , I"",. 100, 10U, 17.5, Plate. artificially twinned quart*. 13<J; Bcrtnind, 137; 
100; c 
M ierorefrartomcler, 95. 
Microscope, field of, 4'.'; lens system, optical ele- 
ments of. 4'l: objective, 4'.i; resolving power of 45; 
shield, convenient furm of, .'t'.i; >ttind, 11. 
\licu Icsru. ri-i <li termination, *3. 
Monochromatic M.-u. 
Monochromatic light. 21. 
Muller-Pouillet, l.chrbuch <1. Physik. 10. 
:!, measurement^ on, 112, 103; optic axial 
until' I '.''. 
Nakamura. quartz half-shade plate, 139. 
\cwton. (..lor M-ale. Ins. 112. M.I. 133. 
Nichols, inten.-ity of daylight, S7. 
Nirol. lower, 11; pri.-m>. ,":."i; iot:ili.in of upp<>r, 141; 
upper, II. 
Nikitia. oompetUBtor, 104; graduated porcelain hcmi- 
.-phcre. Inti. 173, 17(1, 1 Ml, 200. 
Nodal pl-me, 1 v 
Normal magnification, 41. 
Numerical aptTturv, : 7,47,48. 
Nuiiit-ricul aperture, determination of, 51. 
Numerical aperture, physical significance of, 42. 
Nutting, acknowledgment to, 9; colorimeter. 70; 
color .scale, ft'.); luminous equivalent of radiation, 
visibility of half-shade apparatus, 139; 
specific rotation of quartz, i:;l; standard while- 
light, 108, 109, 110, 112. 
( >bject field of view .stop, 34. 
< >bject glasses, spherical, 177. 
Objective, achromatic, 33, 49, 51; apochrorr.atie, 33, 
50, 51; clamps, 00; correction of microscope, 31); 
dry, 50; determination of numerical aperture, 51; 
immersion, 50; microscope, 11, 49; me-i.sure for 
revolving power of, 45, 46; oil immersion, 38; 
,i-apochromatic, 50.51. 
( >lih<|iie illumination, ."..!. '.Hi. 
( (cular, Bert rand. 140; bi-nicol, Io7, 145; Caldoron, 14fi; 
i"impcns:iting, 52; coordinate micrometer, 155, 100, 
171, 175; C'zapski, 171; double-screw micrometer, 
155. If*. 175. 1%; lluyiicns, 52; micm-scope, 11; 
projection. 05; Harnsden, 52. 
Optic axes, dispersion of, 82. 
Optic axial angle, 7, 8, 69, 147; measurement of, 152, 
155, 172, 194, 195, 196, 197, 198, 199; measurement 
of, I iv means of extinction angles, 19!; measure- 
ment of. by means of relative birefrinuence of 
known section. I'JH; measurement of. on plate per- 
pendicular to optic normal, IMi: im-isurement of, 
on section normal t-i obtuse bisectrix, 1N7: mi-a.s- 
urement of, on total refracliiini-ler. li);!; methods 
for measurement of, 199, 2<X); relative accuracy of 
different me! lmd> for measurement of, 104; uni- 
I vi-iife DMihodl for measurement of, IV. 
( )pticaxis, determination of position of, 17S. 
Optical character, determination of. 74; of bircfracting 
minfrals,74; of elongation, 7, 69; of mineral, 7, 6!>; 
on plate perpendicular to acute bisectrix, determi- 
nation of, 7S; on plate parallel to plane of opi.. 
determination of, 79. 
Optical carves, 179. 
Optical elements of microscope lens system, 49. 
( )pti>-:il system of petrographic microscope, 1 1 , i:. 
( )rthographic projection. 63, 65, 66, 67. 
t Irthoconal projection, 6." 
( irthomorphic pnijection. 
Overcorrection, chromatic, 31. 
Outline picture, 53. 
Parallel projiM-tion, Ci5. 
Paraxial ray?. 14. 
I'uuly, refractive Index of liquid 
Pearce, Trait d. Tech. Min. et IVtr., '.., 105. 
Pellet in. A., geometrical optics, 1". 
Peiilii-ld, Ptereographic projix-ti'in, ti4. 
I'errot, meamirement of refractive indices, 98. 
Perspective pnijection, 64. 
Pctronraphic microscope. accurate measuring device, 
57; adjustment of, 11, 12, 01; construction of, 11; 
mechanical system of, 11; optical system of, 11, 
13; purpose of dcsien, 10. 
PeUval condition. 21 , 30. 
Photographic lens, correction of, 30. 
Plogioclasc feldspars, optical determination of, 7. 
Plane polarized light, 13. 
bi quartz wedge. H'-i. Ill), 146; Hravai-8t6>NT, 
134, 145; Hrezinn, 112. ( 'alden.n ralfite. 135; half- 
sbade, Nakumura, l.i'.i; KO|M>||, 142; Koenip- 
berger. 103. 134, 145; quarter undulation of II. 
Tr.uil,e, 135; mwitive tint. 5. 133, 145. 146; 
Truubc, 145; twinned quartz, 145; twinned si-le- 
nne, 136. 
Platform, mechanical, 12. 
Pleochruism, 7, 69, 71. 
PiH-kels, meusuremcnt of refractive indices, 99. 
Polarized light, convergent, 13; plane, 13. 
Polarizer, 11,55. 
Postel projection, 67. 
Preston, theory of light, 116, 118. 
Primary color, 51. 
Primary spherical aberration, 51. 
Principal focal length, 17. 
Principal planes, 18. 
Principal rays, 34. 
Principal zone, character of, 71. 
Probability of encountering sect ions suit able for optic 
axial angle measurements, 189. 
Projection angle, 34; plats, 166. 
Projections, 63. 
Pulfrich, total refrnctometer, 193, 124. 
Quarter undulation plate of H. Traubc, 135. 
Quartz, birefringence of, 112; circular polarization of, 
112; plate, artificially twinned, 63, 136; wedge, 
artificially twinned, 63; wedge, graduated, 101,102. 
Quincke, color scale, 111. 
Radde, color scale, 69. 
llamsden disk, eye-piece, 35; ocular, 54, 150. 
Kay s, central, 14, paraxiul, 14. 
Reflector, 11. 
Reiche, image formation in microscope, 42. 
Renard, microchemical reactions, 69. 
Rendtorff, rotation of quartz, 112. 
Refraction at a single spherical surface, 14; through 
a lens, 15. 
Refractive index, 7, 8; determination of, 92, 99; 
direct measurement of, 98; of Canada balsam, 
91; of mixtures, 92. 
Refractive indices, 69, 83. 
Refractive liquids, 86,97,98. 
Refractometer, total. 97, 99, 100. 
Resolving power of microscope objective. 45. 
Rinne, interference cross in objectives, 76, 159. 
Rollet. color wale, 111,112. 
Rosenbusch.Mikros. Physiographic, 9, 10, C9, 71, 79, 
81, 105, 140, 194. 
Rotation of nicols, simultaneous, 57,58. 
Rotation of plane of polarization, 74. 
Rotation of upper nieol, 141. 
Sagittal plane, astigmatism, 29. 
Schaller, refractive index Canada balsam. 91. 
Schi.-'toscop, Briicke, 70. 
Schmidt, Babinet compensator. 101. 
Schnittweite. 111. 
Sehott, on projections. 63. 
Schrnuf, Brezina plate. 14-'. 
Schroeder v. d. Kolk, condenser, 173; hemisphere, 
174; immersion method. 93, Ha; interference fig- 
ures, 74; oblique illumination, 85. 102. 
Sehronrock, half-shade apparatus, 141. 
Schuster, A .optics, 10. 
Schuster, M., extinction angles. 132. 
Secondary spectrum. 32.50.51. 
Selenite, birefringence of, 112; twinned plate C3, 136. 
Semi-apochromatic objectives 49, 5O, .11. 
Senarinont, measurement of birefringence. 103. 
Sensibility, adjustable !>. 
Sensitive tint plate, 58, 73,133, 145, 14fi; Rravais. 103. 
Sensitiveness of extinction angle methoils. 142, 143. 
Shacreened surface. 91. 
Siexlentopf, wedge, 101, 1(12 
Sicthi;lT, ten, condenser lens. 173. 
Simultaneous rotation of nicols, 57, 58. 
Sine condition. 21.26.2S.49.50. 
Skiodroms. 81. 
Smith-Helmholx equation, 15. 
Sommerfoldt, condenser apertometer, 172; device 
for rotation of nicols, 57. 5S; selenitc plate, 63, 
136; suggestion for combination wedge, 102. 
