This crossbow was suggested as a major weapon of war and, in Leonardo's mind, it was to be employed for shooting large arrows against the enemy ranks and create havoc among them. In order to increase its flexibility and power, the gigantic bow was to be manufactured in several lamellar sections. The shooting rope was stretched with a mechanical device and was then released by percussion or through the action of a lever. The six carriage wheels could be inclined, so as to ensure greater firing stability. OGIVAL PROJECTILES
These models have been made to highlight Leonardo's remarkable intuition on the effect of air on projectiles fired by cannons. Although he did not develop a mathematical theory on trajectory, the wings and the particularly modern shape of the projectiles are grounds enough to assume that he had correct intuitions on the attrition action of the air and the importance of an aerodynamic shape to ensure trajectory stability and firing efficiency. AUTOMATIC IGNITING DEVICE
This model testifies to one of the ideas Leonardo developed in order to improve the ignition of firearms. The device is made up of a coil spring, linked to a wheel above by a chain. The wheel, rotating, strikes against the flint (on the left) and produces a spark. The trigger is on the right. The three-link Chain for automatic igniting device has been reproduced on a larger scale and built into a separate model. Water and Land Machines

DIVING BELL
Envisaging a diver’s prospective activities, Leonardo tried his hand at giving detailed descriptions of the outfit needed and of its workings. For usage at war, he conceived of simple head-coverings fitted with undersized snorkels, and of webbed gloves and flippers for a diver to wear.

DRILLING MACHINE
The double-movement drilling machine was conceived by Leonardo before his arrival in Milan. This machine made deep drilling and digging possible. It worked in the following way: the drill was driven into the ground by rotating the upper bar, while, by rotating the second bar, the drill was heaved back up without turning and it lifted out of the ground all the earth which had collected on it. BOAT WITH PADDLE WHEELS
Leonardo envisaged the driving paddle wheels of a boat being about 90 cm long. The wheels intended to magnify the oarsmen’s strength were designed as being about 60 cm in diameter, and fitted with 16 cogs that engaged with a sprocket wheel of about 15 cm in diameter fitted with 12 cogs.