Mouchette wheel

German calls this form Fischblase or Schneuß, and English the mouchette: round at one end, running to a point at the other. Two, three or more of them turn together in a circle, most often in the tracery of late Gothic. John Henry Parker wrote in 1881 that the English Perpendicular is known by the upright lines of its tracery, while in all the styles abroad those lines flow like flames, “and for that reason they are called Flamboyant”. The record gives the form, not its working, so the construction here is our own, and it is exact. The compass walks the rim at its own opening, and every second mark stands a third of the round from the next. The chord between the two marks beside the first halves its radius, and the circle about the centre through that half cuts the other two radii. About each of the three points so found, a circle of half the radius passes through the centre and touches the rim. Each mouchette is one of these circles with the space left between it, the next circle and the rim; its tail runs out where the next circle touches the rim. Where the circle of half the radius about the centre crosses the first of the three, the line through the two crossings halves that radius once more, and at the quarter so found a ring stands in every head, an eye. The three are equal, each a third of the window.