Beyond Archimedes: Stevin’s Elements of Hydrostatics

Abstract

The content of Stevin’s hydrostatics was original and became a cornerstone of the advances in hydrostatics that were to follow it. Stevin grasped the fact that the force on a solid surface in contact with water is independent of the orientation of that surface and depends only on its depth beneath the uppermost surface of the water. Some of Stevin’s proofs were highly ingenious. However, his postulates, the most significant of which acknowledged that the depth to which a vessel sinks is proportional to the weight it carries, were insufficient to yield the content of his theory as deductive consequences. In a way that he did not make explicit, Stevin inserted into his theory features of the behavior of water with which he was familiar as a hydraulic engineer but which were not licensed by his postulates. For instance, he assumed, rather than proved or explained, that water presses horizontally against a vertical surface, a phenomenon with which Stevin was familiar through his dealings with lock gates. It was only during the course of the seventeenth century that the facts about hydrostatics identified by Stevin were explained and adequately theorized. Those developments required the recognition that experiment needs to be read as supplying evidence for hydrostatics rather than as being mere applications of it, as Stevin had assumed.