Crossbows, catapults and the scorpion engine
Multi-bow crossbows, a four-bow battery, and the scorpion as machine and poisoned arrow
This crowded sheet, headed 'on motion', assembles a whole armoury of missile engines: single- and multi-bowed crossbows, a four-bow battery, a catapult, the rohmphea, and the scorpion. Leonardo notes that arrows shot from a crossbow-drawn bow fly far and are made almost wholly of iron to be heavy, and that thin bows take a better temper than thick ones. He describes firing four large crossbows, twelve braccia or more each, together for effect. A long antiquarian note explains the scorpion both as a stone- and dart-throwing machine and, following other authors, as a poisoned arrow of human blood and serpent venom said to come from the Scythians or Crete, fit only to be used against traitors.
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Crossbow drawn by a crossbow
A bow that is drawn together with its arrow at the moment of release by a crossbow will, Leonardo says, send the arrow a great distance. The arrows are made almost entirely of iron so that they are heavy.
Crossbows with several bows
A crossbow with much elevation drives its arrow far. Leonardo remarks that the thin bows are given a better temper than the thick, citing the example of the middle of the anvil.
Battery of four crossbows
Four crossbows are loaded one by one and released together for a good result. Each is to be twelve braccia or more, and if one braccio wide and half a braccio thick they can be given much elevation, some six braccia.
The scorpion: machine and poisoned arrow
The scorpion is described as a machine able to throw stones, darts and arrows, and when large to break the enemy's engines. Other authors hold it to be a poisoned arrow that kills at the least touch of blood, made of human blood and serpent's venom, ascribed to the Scythians or the people of Candia, and fit to be used only against traitors.
De moto: the flight of the missile
The sheet is headed De moto, 'on motion', framing these engines as a study of how projectiles are driven and how far they travel. Leonardo ties range to the weight of the iron arrow and to the elevation or draw of the bow.