“A new form of float for water or alcohol manometers,” with demonstration

Abstract

The float consists of an aluminium cylinder with very thin wall, supporting a writing arm of fine aluminium wire. For manometer tubing of in inside diameter, in. or ¼ in. aluminium tubing 2½ in. long is used. This is bored out until the walls are sufficiently light. In the upper end is forced a solid cap of aluminium with a small hole in the center into which the wire for the writing lever is driven. The lower end is plugged with cork. Both ends are painted over with hot paraffin to prevent leaking. For use in alcohol a somewhat larger tube is necessary. Three crossed hairs held in place across the open arm of the manometer tube by a strip of adhesive plaster keep the writing arm centered with sufficient accuracy.

The value of the float consists in its cheapness, the ease with which it can be made, its very slight inertia, and its convenience in estimating delicate changes in pressure for which a water or alcohol manometer is needed.