On the Efficiency of Early Horizontal Waterwheels

Abstract

cestry and once widespread diffusion were indeed amazingly efficient.1 There is a substantial difference between speculations about drawings and descriptions contained in old books and manuscripts and actual observation and measurement of the performance of working machines as done by Wulff. His factual finding that free jet mills of Persia of traditional construction are capable of delivering a power output of 8-10 h.p. with a coefficient of efficiency of 75 per cent is likely to provoke a stir among historians of technology interested in rationally interpreting the development of man's quest for mechanical power. The Persian mills studied by Wulff are similar to the molinos de bomba that Juanelo Turriano described around 1560.2 Juanelo refers to them as well known, and there are good reasons to suppose that they do not differ substantially from those depicted almost a century earlier by Francesco di Giorgio and Leonardo da Vinci. We do not know for how long they have been established in the East, but if an interdependence exists, transmission is more likely to be East-West than vice versa.