INDEX 715 Hop wood, H. V............... 391 Horizontal objects..........32, 268 Homer’s Zoetrope.........68o, 682 House system for projection microscope................ 285 fusing ................... 83 lamp for.................. 78 Huhbell (Hubbell Inc.) 86-87, 503-505 Huygenian ocular......230, 233, 280 Hydrogen, cylinders........... 103 substitute for.............. 113 Hyperopia or long sight........ 661 Iban A1 Haitem and the camera obscura................ 674 Illumination, dark ground... 647-650 Foucault’s method of... .650-651 Toepler’s method of.....650-651 Illumination, flashes per second at which flicker disappears 424 with high powers........599-601 with lower powers.......... 598 with magic lanterns 16-18,584-587 with moving pictures 411-415, 593-598 with projection microscope 247-256,271,278,284, 286, 287, 328. 335. 346, 598-601. 617-620 Illuminating gas for lime light... 112 for magic lantern.......125-127 Image, brightness of. . 18-19, 612-617 carbons.................. 251 condenser with spherical aber¬ ration ................. 585 condenser without spherical aberration.............. 584 connection with aperture.... 615 correct..........26-27, .371 > 3®7 dim and brilliant in combined projection.............. 177 erect 26-27, »9°. 359. 363-365- 367. 369. 37». 373. 387 with opaque lantern.. 363-365 with translucent screen 26, 362 with two lenses......368-369 formation with, the magic lantern ................ 584 effect of an extended source of light................. 586 moving pictures.....591 -598 point not on the axis..... 617 projection microscope. . .598-601 Image projection microscope with amplifier or ocular. .. .600-601 a microscope objective..... 616 hazy..................... 308 inverted.....26-28, 359-37». 5®4 for micro-projection..... 470 for different microscope tubes 243 for moving pictures........ 468 for opaque projection....... 181 for screen distances......... 466 lantern slides for........... 464 sharpness of..........28-30, 256 size, found by calculation. .. 261 found by measurement 257-260 stereoscopic with the magic lantern ........ 37-39 troubles with screen images 52-57.301,308 Incandescent lamp............ 14 after rheostat............. 17 before rheostat............ »3 testing for voltage......... 46 tracing pictures............ 374 Inclined carbons.....61, 70, 543_550 Indirect room lighting......441-443 Inductor.................352~532 with arc lamp..........352, 532 varying amperage with..... 532 wiring.................352, 532 Infra-red radiation............ 566 Ink for unvarnished slides...... 207 Inks and pens for varnished slides 206-207 Insulation with large currents 5»3-5»4 for long distance wiring..... 513 of wires................497_498 regulating amperage........ 501 Intensity of light, in different directions .............. 563 Intrinsic brilliancy, of crater of arc.................... 564 of the light source 138,564.612-615 of the sun..............»38-»39 Iodized starch polarity indicator 510 Iris diaphragm, effect on cone of light................279, 620 Italian lantern slides.......... 201 Ives, Fred E.—Ether oxygen lime light, history and new ap¬ paratus................. 686