Braziers, a study of the motions of fire, and a curve made square
Furnace sketches with a note that dampers and boiling water drive fire for melting
The verso of f.145 sketches heating apparatus: a domed cover fed by narrow air-vents is described as keeping coals well alight, to be built of copper over durable terracotta, one braccio across and half a braccio high. A note lays out a programme of study — after treating the motions of heavy solids, to treat liquids, air and fire, comparing the whirlpools of air and water and harnessing the drilling motion of fire for meltings by means of dampers and boiling water. The recto of f.142 carries a geometrical figure showing a curve n o b that, when straightened onto the line n f, forms a right angle.
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A covered brazier to keep coals burning
If the air-outlet above and the wind-inlet are both kept very narrow, the coals will stay well alight. The cover should be of copper, one braccio in diameter and half a braccio high, and the rest of terracotta durable in fire.
Programme: the motions of solids, liquids, air and fire
After treating the motions of heavy solids, Leonardo tells himself to treat heavy liquids, air and the motions of fire, and to compare the motion of fire with the whirlpools of air and water. He looks for drilling motions of fire, made powerful for meltings by its revolutions, achieved with dampers and boiling water.
A curve straightened into a right angle
The curve n o b joins the semidiameter, and b meets it at a right angle; when the curve is straightened and flattened onto the line n f it will make a right angle.