Copper-melting furnace and embryonic umbilical studies
A wasps'-nest furnace to found copper, the cord binding child to womb, a proportional compass and a sum
On blue paper, the upper half shows a tall round furnace throwing off feathery flames, drawn both outside and in section, for melting copper. Leonardo specifies a tower four braccia thick, pierced all round with holes like a wasps' nest, its wind-pipes shaped like pyramidal cones, fed with continuous charcoal for a 'condensed fire.' Turned ninety degrees, the sheet also carries a proportional compass ('the compass of proportion'), two small anatomical drawings of the umbilical cord binding the child to the womb, and, upside down, a worked arithmetical calculation. The several studies sit at different orientations across the leaf.
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Furnace for melting copper
The furnace is a round tower four braccia thick, pierced all round with holes in the manner of a wasps' nest, its wind-pipes all of one form like pyramidal cones. Charcoal is fed continuously for a 'condensed fire,' the exterior labelled with firewood and the purpose 'to melt copper.'
The umbilical cord binding child to womb
The navel, Leonardo writes, is the ligament of the child with the sheath that clothes it, which ramifies and binds itself to the womb — like a button with its buttonhole, or a burr clinging to a burr. Two small anatomical sketches accompany the note.
The compass of proportion
A proportional compass is drawn and named 'the compass of proportion' (sesto della proporzione), an instrument for scaling measurements up and down.
A worked arithmetical calculation
Turned upside down, the sheet carries a column of figures — 1, 17, 554 and 1000 giving 58 1/14, with the further numbers 177, 17, 1, 440, 58 and 1020 — a worked calculation.