Draper's Experiment simplified

Abstract

WISHING to repeat Draper's Experiment, and casting about for a simple method of performing it, it occurred to me to take advantage of the intense heat evolved in the combustion of sodium, and, beginning with the entire spectrum, watch its degradation as the heat declined; to which end I formed a shallow, conical cup of thin copper wire, half an inch in diameter, and, putting therein a piece of sodium, applied a spirit-lamp till it burst into flame; very soon the mass melted and rose to an intense, white heat, the air streaming in through the spiral greatly favouring the combustion, a full spectrum of the utmost purity and splendour was formed, which continued as long as the white heat lasted, but afterwards declined from, and rapidly at, the violet end through the whole spectrum to the red, which persisted longest. On repeating the experiments, and raising a very narrow slit to the spectroscope, I found, as I anticipated, the sodium line reversed, and I had before me a miniature sun, a glowing centre emitting light of every wave-length, while the melted sodium, flowing through the intervals between the wires of the lower part of the cone and being dissipated by the heat, surrounded the liquid centre with an atmosphere absorbing light of its own refrangibility.