What Exactly Was Torricelli’s “Barometer?”

What exactly was Evangelista Torricelli up to when, in 1644, he took mercury filled tubes and turned them upside down in other mercury filled tubs? A canonical story anchored by the larger historiographical edifice of the “Scientific Revolution” holds that Torricelli was using a new instrumental experimental approach to natural philosophy to demonstrate and measure the weight of atmospheric air. Within this frame, Torricelli’s mercury esperienza as he called it heralds the birth of modern experimental science through his invention of the first modern barometer. This paper questions this traditional narrative by re-interpreting the archival foundations upon which this account is based. In particular, it stresses the gaps between the rather slim documentary record of Torricelli’s work and the canonical interpretation of it built by the “Scientific Revolution” literature. It also uses other documentary contexts available in the same archive to give a different, though insistently historical, account of Torricelli’s motivations for and conceptualization of his labors. The paper does not conclude by claiming a new and definitive revisionist interpretation of Torricelli’s mercury esperienza, but by suggesting instead that the emphatically historical but also interpretively flexible approach to Torricelli’s work pursued in this paper exemplifies a “Baroque” approach to the history of science, one that can be useful in generating fresh interpretive insights about the early history of modern science.