Grain mill, furnaces, and a concave burning mirror
Studies of a milling machine, kiln and furnace construction, glazing a clay sphere, and a sun-focusing concave mirror
This crowded sheet gathers several technical studies. At the top a machine for grinding grain stands beside a smaller turned disc, while other drawings show furnaces (fornello) in plan and external view, with labelled parts (foundation, bung, bath, air-vents and fire) and instructions for making, firing and thickly glazing a clay sphere. A geometric construction with the points d, e, a, b, c sets out how to shape a concave 'sphere' that, turned to the sun's rays, would burn whatever is placed at its focus, the profile drawn round like a sugar-loaf cone. A further note observes that the longer the natural motion of fire or of a weight, the greater its percussion.
On this page
Machine for grinding grain
A tall machine drawn at the top is labelled a 'way of grinding grain,' pairing a large driving wheel with a millstone and press. A small turned disc stands beside it.
Firing and glazing the clay sphere; mould case (a)
The sphere is to be made of clay, fired, returned to the instrument, then thickly glazed and set upside-down in the furnace on flat ash so that the glaze runs quickly. A case marked a is noted as where the closed mould is shut.
Concave sphere to burn with the sun's rays
To make a concave sphere that, turned to the sun's rays, burns whatever is interposed at its focus, one first makes a pyramid (cone) as figured, round in height like a sugar-loaf; the mirror's curve is derived from this cone.
Constructing the mirror profile (d, e, a, b, c)
The construction requires that e d enter twice into a b; then half of the line d b, which is e, is cut to the centre of the pyramid's base, c, and that cut yields the template (centina) for the curve.
Furnace (fornello): parts and air intake (a-b)
A furnace is drawn in plan and external view with its foundation, bung, bath, air-vents and fire labelled. Tiny letters mark the air mouth: from a to b the passage must be hollow so that the air itself gives movement to the fire.