Charles March was a carpenter rather than a millwright, and this may account for the unusual construction of the mill. Originally it had a single storey octagonal brick base with a second storey constructed of wood; this housed all the working machinery. Above this was a conical tower which held the post supporting the cap on which the sails were mounted.
The post was hollow so that an iron shaft could be taken down inside it to turn the millstones on the floor below. It was therefore known as a hollow-post mill. Such mills are common in Holland, but most unusual in this country. It happened that a mill of this type existed in Southwark, near the site of the old Globe theatre, so it is presumed that Charles March copied this design, being ignorant of more usual windmill practice.
The sails, which had a span of about 15m, were mounted on a cast iron shaft 2.4m in length which also carried a 1.8m diameter iron wheel with wooden cogs; this drove a smaller bevel gear known as a wallower, mounted on the top of the vertical shaft which ran down the inside of the hollow post. The larger wheel was known as a brakewheel as it could be clamped by a wooden collar when it was needed to stop the sails turning.
The main shaft drove the great spur wheel on the ground floor, from which two smaller gearwheels (known as spur nuts) took the drive back up to the first floor where there were two pairs of millstones 1.3m in diameter. In each pair the top stone turned while the bottom stone remained fixed, grinding the grain as it passed between them.
The whole cap carrying the sails rotated round the post so that the sails could be turned into the wind. This was done automatically by a series of gears driven by the fantail mounted on the back of the cap. The sails themselves were of the patent type with opening shutters controlled by striking gear operated by a chain hanging from a wheel below the fantail staging.
Click here to download a diagram of the windmill as it was in its working days.