Stephen Hales, English botanist and chemist, mid 18th century.
© Science Museum / Science & Society Picture Library
Engraving made in 1800 by Hopwood after a painting by Coutes, of Stephen Hales (1677-1761). Inspired by the experimental philosophy of Sir Isaac Newton (1642-1727), Hales' work 'Vegetable Staticks [sic]' (1727) became the foundation of plant physiology, setting the standards in the methods of biological experiments. Hales' most important work concentrated on the water balance of plants and was the first to measure root and leaf suction and root presure which led to discusions regarding blood presure and the circulation of blood. Amongst other practical apparatus, Hales invented machines for distilling sea water and preserving meat.