"Safety-first" Candle.
Candles can easily be fitted with attachments to put out the light at a set time. Mark a candle of the size used and time how long a certain length of it will burn. Then suspend a small metal dome or cap, to which a string is attached directly over the flame, and run the opposite end of the string over nails or through screw eyes, so that it can be tied around the candle such a distance from the flame end that the part between the flame and the string will be consumed in the time desired for the light to burn. When this point is reached, the string slips off the candle and the cap drops on the flame.