The Tubular Lantern: A Flame That Breathes Through Its Own Frame

"The object of this invention is to improve upon my tubular lantern heretofore patented, as regards simplicity and cheapness, so as to be able to meet any demands there may be for a cheap lantern; and I have also attached a thumb-piece to the movable top of the lantern, to facilitate raising it to remove the globe or glass." The invention consists "in inserting the air-tubes C into the top of the air space B", avoiding elbows. A is the oil-pot and B "an air-chamber on the top of the oil-pot, which serves the double purpose of keeping the oil in the oil-pot cool". The globe-holder F hangs from "the inverted-saucer shaped air-gatherer P", raised and lowered with it; a spring H and thumb-piece I let the user lift it "with the thumb or one of the fingers of his hand with which he holds the lantern". "The currents of air passing through this lantern are the same as in my tubular lanterns heretofore patented, and need not be described here".

Outdoors or in a well-ventilated room on a non-flammable surface, fill a hurricane lantern with lamp oil, trim the wick flat and light it low. Turn the wick up until the flame is steady and does not smoke. Set a fan a metre away and raise its speed step by step. Note when the flame flickers, when it smokes, and whether it goes out. Then shield the top of the lantern with a sheet of card held well above the chimney and repeat: the draught changes as the air at the inlets is disturbed. Measure the wind at the lantern with an anemometer.

**John H. Irwin** of Philadelphia received US 99,442, dated 1 February 1870, improving his earlier tubular lantern with tubes entering the top of the air space and a thumb-piece to lift the globe-holder. **Honest limits.** This patent does not describe the air flow itself; the notebook's draught model is the general principle, with example temperatures and fuel rate.