lue, 120
Flexible couplings, 77
Frequency meter, 65
Friction brake, 88

{142}
High speed telegraphy, 70
Hughes governor, 65
Hughes printing telegraph, 63
Hurter and Driffield, 104
Hydrogen, 100

Incidence, angle of, 127
Inertia, 64, 65, 111
effects in photo-telegraphy, 110
method of counteracting, 103, 112, 113
effect of wave-length of light on, 114
Intensifying solution, 122
Isochroniser, 89, 91
details of, 91, 92, 95
Isochronism, 64, 69, 70, 71

Kathode rays, 53
Knudsen, 2
apparatus of, 9
Korn, 30, 33, 45, 65, 72
apparatus of, 31

Lamps, coloured, 94
Lenses, 85, 125, 128
principal focus of, 130
conjugate foci of, 131
action of, 129
convex, 128, 131, 136
concave, 128, 138
focal length of, 130, 138
aperture, 138
meniscus, 139
Light, diffusion of, 86
extraneous, 87
Limit of error in synchronising, 64
Line balancer, 3
Line screens, 9, 15, 16, 116
making, 116

Magnifying power, 136, 137
Marconi valve, 44, 54
coherer, 40
Mechanical inertia, 33
Mercury break, 81
churning of, 82
containers, 82
Mercury jet interrupter, 29
Metal prints, 15, 18, 32, 59, 64, 95, 120, 124
drying the, 121, 123
exposure of, 121
size of, 22, 24, 75, 77
pressing the, 22
Microscope, 131, 137
Military uses, 35
Mirror galvanometer, 9, 42, 73
Mirror, 47, 51
Morse code, 35
Motor speed, 89, 95
driving, 91, 93, 95
clockwork, 63
electric, 63

Nernst lamps, 43, 85, 98
heater of, 99
filament of, 99
principle of, 98
resistance of, 100
efficiency of, 101, 102
overrunning, 101
Nicol prism, 53

Paper for electrolytic receiver, 56
Parabolic reflector, 8
Period of galvanometer, 43, 44, 46
_Photographic Daily Companion_, 105
Photographic films, 40, 43, 45, 53, 54, 62, 85, 86, 98
process, 37
chemical inertia, 103
exposure of, 103, 107
speed of, 104, 105
plates, orthochromatic, 59
plates, 120
Points to be observed in preparing metal prints, 123
Poulsen Company, 32, 47
arc, 31
Preparing selenium, 109
photographs for transmitting, 15, 115
sketches on metal foil, 124
Prism, 128
action of, 129
Process plates, 122
Professor Nernst, 98

{143}
Radio-photography, requirements of, 74
Refraction, angle of, 127
Refractive power, 127
Relay, 25, 39,