Acquired in 2024
What is movement? What defines it? Is there something in common between each step, graceful leap, or fall, or the swaying of a tree or flow or a river? How can these be explained by the laws of nature? These were the questions that spurred the research of Giovanni Alfonso Borelli (1608–1679) and led to “De motionibus naturalibus a gravitate pendentibus” (“On Natural Motions Due to Gravity”). Published in 1670, Borelli’s work ventured into uncharted scientific territory, blending mathematics, physics, and biology to reveal a grand vision of a natural world governed by gravity.
Born in Naples, Borelli studied under some of the great minds of his time, including Benedetto Castelli (1578–1643), a student of Galileo Galilei (1564–1642). Borelli was deeply influenced by Galileo’s approach to understanding natural phenomena through mathematical and experimental methods, and this shaped his own scientific investigations. Over the course of his career, Borelli held academic positions in various Italian cities, including Messina, Pisa, and Rome, and became associated with scientific academies like the Accademia del Cimento, which was devoted to experimental science.
While primarily a physiologist, his work “De motionibus” turned out not only to be a foundational text of modern biomechanics but also one of the most significant contributions to our understanding of fluid dynamics. In this treatise, Borelli explored the movements of fluids in relation to gravitational forces, attempting to explain the natural behaviour of fluids in motion, such as water and air. He applied mathematical reasoning to these problems, which was a relatively novel approach at the time, quantifying and measuring flow in different circumstances.
In the book, Borelli takes up hydrostatics, looking at siphons and pumps, and presents an approach to understanding the expansion of water while freezing. Among his most important contributions is his treatise on capillarity, and his investigations on the action of capillary tubes, in which he identifies that the height of the ascent of liquids in the tubes is inversely proportional to their diameters and independent of external forces such as the pressure of air or gravity. Understanding capillarity gives insight into many natural processes, such as the spread of blood in a body or fluids in the stem of a plant. Yet it is also crucial for environmental and engineering applications where fluid movement in narrow spaces is a factor, such as in special fittings and filters.
“De motionibus” is more than a treatise – it’s an invitation to marvel at the natural order and to see gravity not as a constraint but as the defining force of the universe. Borelli's contributions to biomechanics and fluid dynamics represent significant advancements in the application of mathematical principles to the natural world. This is the first book by him in the Iron Library. This interdisciplinary work laid the foundation for numerous future scientific developments in physics, biology, and physiology, cementing his legacy as one of the key figures of the Scientific Revolution, alongside Galileo, Descartes, Newton, and Boyle, works by whom are also to be found in the library’s collection.
The title page of Borelli's book.
The parchment-bound volume on the shelf in the Iron Library.
Giovanni Alfonso Borelli in academic costume (Wikimedia Commons)
Simple and to the point: one of the many small diagrams explaining Borelli's observations of flow.