A form of adjustable sundial invented by Michael Butterfield, an English instrument maker who is known to have worked in Paris between 1678 and 1680. The Butterfield sundial is a small, portable horizontal sundial with a baseplate, usually octagonal but sometimes oval, of brass or silver, with engraved hour lines and a small inset compass. Four or more concentric sets of hour lines are employed, each for a definite latitude, and the folding gnomon has a pivoted style edge, which slides over the main gnomon, so that the angle of inclination of the edge can be varied. The fixed portion of the gnomon carries a scale of latitudes; the pivoted portion is engraved with a bird, the tip of whose bill indicates the inclination on the latitude scale.