This is a most intense flash-light used for military signals. Three parts finely powdered resin are mixed with one part magnesium dust, and blown by means of a tube through the flame of a spirit lamp. The flame should be large so as to insure the ignition of all the dust. The distance at which such a flame can be seen is extraordinary.

Some years ago the author devised a method of producing a light of marvellous brilliancy by the use of magnesium powder. A rude argand spirit lamp was constructed in such a way that the central tube could be connected in an air-tight fashion with a reservoir of oxygen. A small stopcock, with the hole of the plug closed at one side so as to leave a cup instead of a hole, was fitted into the tube leading from the oxygen reservoir to the lamp. When turned upward this cup was easily filled with magnesium powder, and when turned down it of course dropped its charge into the stream of oxygen, which carried it at once to the lamp, there to be consumed it a flash of extraordinary brilliancy.