‘The Curious Ways to Observe Weight in Water’: Thomas Harriot and His Experiments on Specific Gravity

Abstract

Abstract This paper explores the experiments of the English mathematician Thomas Harriot (1560-1621) on specific gravity in the years 1600-1605, as recorded in a series of manuscript notes in British Library Add. MS 6788. It examines the programme of reading undertaken by Harriot before (or during) these experiments (including works by Jean Bodin, Giovanni Battista della Porta, Gerard de Malynes, Gaston du Clo, and Juan Bautista Villalpando), and describes a series of experiments conducted by him which compared the weight of a wide variety of substances in air and water. Harriot’s work is compared to that of his contemporary Marino Ghetaldi (1568-1626) in Promotus Archimedis (1603), and the work of both mathematicians can be positioned in the context of sixteenth-century mathematical responses to the famous problem posed by Hiero, King of Syracuse to Archimedes (as related by Vitruvius). Harriot’s use of proportional mathematics (especially the “rule of alligation”) in his experimental work and his application of this technique to problems in the alloying of metal and chymical analysis is examined in detail.