Herr Hefner-Alteneck has suggested a new standard light for
photometric purposes, which promises to be very simple and effective
in operation. The light is produced by an open flame of amyl-acetate
burning from a wick of cotton fiber which fills a tube of German
silver 1 in. long and 316 mils. internal diameter; the external
diameter being 324 mils. The flame is 1.58 in. high from top to
bottom; and it should be lighted at least ten minutes before using the
light for testing. A cylindrical glass chimney surrounds it to ward
off air currents. About 2 per cent. of the light is absorbed by the
glass. The power of the flame is that of a standard English candle;
and experiments have shown that amyl acetate, which besides is not
expensive, is the best fuel for steadiness and brilliance. Neither the
substitution of commercial amyl-acetate for pure nor the use of a wick
of cotton thread for loose cotton fiber alters the illuminating power;
but the wick should be trimmed square across the mouth of the tube,
for if it project and droop the illuminating power is increased.
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[NATURE.]