Catapult with its spring-loading device
The ancient catapult of Nonius and Pliny, driven by twisted sinews and a steel spring
Headed 'on motion', the sheet studies the catapult. A large mechanism at the top shows the spring-loading device, a great wheel geared to a toothed roller that draws and holds the arms, while a smaller catapult is drawn below and a small arch labelled 'first' sits at the upper left. Leonardo notes that a feathered iron arrow flies fast. A longer passage, citing Nonius and Pliny, describes the catapult as an ancient engine that shot a three-cubit dart with a three-faced iron head, launched by timbers released from the constraint of twisted sinews, and adds that a piece of steel returning to freedom can swiftly drive off a dart.
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The catapult after Nonius and Pliny
Following Nonius and Pliny, the catapult is described as an ancient engine that shot a dart of three cubits with a three-faced iron head. The dart was driven by timbers released from the constraint of twisted sinews.
Spring-loading device of the catapult
The large drawing shows the mechanism that arms the catapult: a great wheel geared to a toothed roller which draws back and holds the throwing arm. A detail at the left isolates the toothed roller.
Stored elastic force drives the dart
Leonardo notes that a piece of steel returning to freedom can swiftly drive off a dart set against its course, the same principle by which twisted sinews and bent timbers store and release force. The heading De moto frames the page as a study of this motion.
Feathered iron arrow
A short note beside an arrow states that this arrow, if made of iron and feathered, will fly fast.