“Del colpo cagion del foco” (Codice Atlantico, f. 973v). A dialogue between natural philosophy and mechanical arts in the manuscripts of Leonardo
Italiano

by Andrea Bernardoni

Saturday 11 April 2015, 10.30 am
Vinci, Teatro di Vinci

In Leonardo’s natural philosophy, percussion is the final effect of force, the cause of mechanical changes in bodies. Instead, of the four natural elements, fire is the one that has the power to transform “quasi tutti i corpi di suo essere in un altro” (“almost all bodies from their own nature into another”, Codex Atlanticus f. 1033r). Leonardo offers various examples of the causal link between these two “potenze di natura” (“powers of nature”) that put the physics and chemistry of the four elements on the same plane. Hammer blows on an anvil bring about an imbalance in the structure of the material being percussed, producing heat to the point at which a match can be lit. In the heart, blood beats against the walls of the ventricles, heating up to the point of transforming everything into fire if, that is, fresh air from the lungs were not to intervene to maintain the thermal balance (RL 19081r). In metallurgical blast furnaces the smelting of metals depends on the “moti trivellanti” (“drilling motions”) of fire and the speed of their impact with the metal (Codex Atlanticus f. 87r, Codex Arundel P 29r: f. 149v).
Tracing a path through themes in natural philosophy intertwined with technical processes, an attempt will be made to shed light on Leonardo’s physics and technology of fire. He first began to engage with such issues while training in Verrocchio’s workshop in Florence. In his time in Milan, especially during the 1490s, he conducted important experiments in internal ballistics, trying to understand the physical and chemical dynamics of the explosion, and took an interest in foundry work in order to grasp artillery production techniques and to develop the method for casting the monument to Francesco Sforza, on which he was then working. Between 1502 and 1508, in the mature phase of his studies of the four elements, Leonardo even reached the point of trying to rethink the notion of the element, attempting to move beyond the merely qualitative dimension of the Aristotelian tradition and conceiving of the element as having physical properties, measurable, at least in principle, in terms of weight.