316 



INDEX 



Electric illuminants, 88, vide Nernst, 

 Mercury-vapour and Arc light, 

 difficulty from small area of, 107, 

 169 



English model microscope, 7 



English tube-length, 40, 151 



Enlargement, distance of lens from 

 focussing-screen for, 306 



Eosin, 214, 216, 294, 299 



Ether vapour, substitute for coal 

 gas, 81, 84 



Evenness of illumination, 69, 147, 

 149, 162 ; importance of, 169 



Exposing, method of, 189 



Exposures, 222 ; by sensitometer, 

 222 ; based on working N.A. of 

 objective, 223, Dr. D. J. Reid's 

 method, 224 ; by exposure-meter 

 (Wynne or Watkins), 225; as 

 depending on illuminant, 77. 79, 



226, on speed of plate, 227; with 

 colour-screens, 219, 227 ; under- , 



227, 233; over- , 227, 232, 233; 

 in printing for lantern-slides, 242, 

 244, 247 ; for coloured lantern- 

 slides, 277, 278 ; in metallography, 

 265 ; in bacteriological work, 272 



Exposure-meters, Wynne or Watkins, 



225 



Eye-pieces, vide Oculars 

 Eyes, use of, to avoid fatigue, 147 



FACTORIAL method, 230 



Filters for light, vide Colour-screens 



Filter-yellow K screen, 211, 214, 289, 

 293, 296, 299, 302, 304 



Fixing, 229, 231 ; in lantern-slide 

 making, 244 



Flatness of field, 25; tests for, 29 



Fluorite, 20, 51 



Focal length of objective, 24, 26, 33, 

 50, 193, in stereoscopic work, 274 ; 

 of condensers, 49 ; and magnifica- 

 tion, 194, 195 



Focus, depth of, vide Penetration 



Focussing, preliminary visual trials, 

 146, 150 ; with immersion objec- 

 tives, 150 ; with achromatics for 

 perfect definition, 152, 153 ; with 

 apochromatics, 192 ; with reflex 

 camera, 140, 141 ; with J. W. 

 Gordon's apparatus, 192; with 

 Leitz micro-metallograph, 143 ; 

 control from a distance, 122, 128, 

 130, 132, 190 ; method of, 190-192, 

 with high-intensity illuminant, 154, 

 191, with ultra-violet light, 254; 

 by projected image on opaque 



screen, 185, 186 ; eye-pieces for 

 186, 187 ; spectacle lenses for, 187 > 

 of metal surfaces, 256 ; of bacteria' 

 156, 191 



Focussing eye-pieces, 186, Swift, 187 ; 

 glass, binocular, 187 



Focussing-screens, ground-glass, 183- 

 185, 191 ; plain-glass, 183, 184, 

 191 ; varnished-glass, 184 ; chemi- 

 cally made, 185 ; - grain of, 183, 

 185 ; insertion in groove, 183, 

 distance from lens for given 

 enlargement or reduction, 306 



Foraminifera, 63, 285, 289 



GELATIN films for colour-screens, 206 ; 

 dry- plates, 218, 219 ; for lantern- 

 slides, 242 



Geometric slide, principles of, 133, 

 136 ; for collecting-lenses, 73 



Gifford F-line screen, 211, 227, 285, 

 289, 290, 299, 300, 303 



Glass, refractive index of, 157, 306. 



Glass colour-screens, 210, 218, 288, 

 291, 304 



Glazing of prints, 241 



Glycerin, 255, 268 



Gordon, J. W., 43, 51 ; vertical 

 camera, 119, focussing with, 192 ; 

 method for dark-ground illumina- 

 tion, 59 ; speculum with light- 

 source of small area, 107 



Grain of focussing-screen, 184, 185; 

 of plates, 218, 219, 245 



Green aniline dyes, 211, 212 



Green colour-screens, 288, 291-294, 

 300 ; for dark-room, 199, 200 



Ground-glass screen, as illuminant, 

 169 ; for focussing, 183, 185, 191 



Gwyer jet, 87 



HALATION, 220 



Heat from illuminants, 70, 77, 79, 

 180 



Heliostat, for sunlight, 108 



Hetley, Messrs., glass for absorbing 

 light, 191, 210 



High-intensity illuminants, danger 

 to eyes from, 154 ; difficulty from 

 small area, 107, means of overcom- 

 ing, 107, 108 



High-power objectives, 19, 28 ; ocu- 

 lar, 34 



High-power work, collecting-lens 

 system for, 72 ; focussing in, 150, 

 191 ; cover-glass thickness in, 154 



Homogeneous system, 19, 35 



Howard Farmer reducer, 236, 245 



