The Float Lamp Extinguisher: A Timer Made from Falling Oil

"Our invention relates to an improvement in automatic lamp-extinguishers, the object being to provide a lamp with attachments arranged and constructed in such a manner that they may be adjusted to automatically extinguish the flame of the lamp at any predetermined time". The float "may be constructed of metal, or in any manner so that its weight shall be of less specific gravity than the oil", inside a casing "having an opening in the lower end thereof for the free admission and circulation of oil therein, thus insuring the same level of oil in the float-casing as exists in the main body of the lamp."

Fill an oil lamp with lamp oil, weigh it, and light it on a fireproof surface away from anything that can catch, never unattended. After an hour, put it out and weigh it again: the loss is the burn rate. Measure the reservoir's inside width and mark the oil level before and after with the ruler. Compare the fall with the notebook, and work out the trigger setting that would put the lamp out after a chosen time.

**Richard H. Frazee, Harvey L. Fisher and Angell J. Hassell** of Toledo, Tama County, Iowa, filed US 211,902 on 19 December 1878; it is dated 4 February 1879. It is a lamp extinguisher, not a candle snuffer. **Honest limits.** The notebook assumes straight-sided reservoir walls and a steady burn rate. Real lamps taper and burn faster with a higher wick. Sizes, rates and settings are examples. Your weighings are the measurement.