rance Company, 227

Trees, 26

Troy, 42

Tuberculosis, 273

Tungsten lamp, 161 _et seq._, 187, 261, 290, 303

Typhus, 273

Ultra-violet rays: 126, 150;
in photographic electricity, 267, 268; 270, 272, 294

United States: petroleum in, 57;
gas-consumption in, 99; 164, 165, 166

United States Geological Survey, cited on sale of gas, 222

United States Military Intelligence, 225, 226

Vacuum tubes, 81, 286

Venetians, 195

Ventilation, 13

Verne, Jules, 143

Vestal Virgins, 42

Volcanoes, 166

Volta, 111, 112, 127

Voltaic pile: construction of, 111, 127

Von Bolton. _See_ Bolton.

War: and artificial light, 11, 178-193

Washington, 305

Water: sterilization of, by artificial light, 280 _et seq._

Watson, Dr. Richard, 67, 68

Watt, 94

Waves: electro-magnetic, 68, 86, 125 _et seq._

Wax, 34, 46, 51

Way: mercury-arc produced by, 124

Wells, 61

Wells, H. G., cited, 148

Welsbach, Auer von: 61;
invention of mantle by, 99, 100, 133

Wenham, 78

West Indies, 25

Whale-oil, 31

Wicks, 35, 36, 53, 54, 58, 59

Winsor, 72, 73.
_See also_ Winzler.

Winzler. _See_ Winsor.

_Wolfram._ _See_ Tungsten.

Wood, 26, 27, 28

Woolworth Building, 302, 303

Wounds: treatment of, by artificial light, 10

X-ray: production of, tubes during War, 131; 137, 150, 270, 280

Young, James: discovers petroleum, 56

Yttria, 85

_Zeitung_, Cologne: 157;
extract from, on street-lighting, 158

Zinc, 125, 130, 267

Zirconia, 84, 85

Transcriber's List of Corrections

LOCATION
ORIGINAL
CORRECTED

Chapter II
and similiar material
and similar material

Chapter XIII
as a constant level
at a constant level

Chapter XIV
the carbons to distintegrate
the carbons to disintegrate

Chapter XV
John Pechham
John Peckham
coated with an allow
coated with an alloy
with various billiant
with various brilliant
key in depressed
key is depressed

Chapter XVI
has nearly doubled
have nearly doubled

Chapter XVII
this own indifference
their own indifference

Chapter XXIII
Nature's lighting varied
Nature's lighting varies

Chapter XXIV
so-called cade