There can be little doubt that 1973 will remain notable as a year in which knowledge of Galileo's mechanics increased dramatically. Professor Stillman Drake's publication, in May, of some of Galileo's early work on the law of free fall was followed in the autumn by the publication of a number of important manuscripts clearly indicating Galileo's use of precise measurement. From a discussion of these manuscripts and Thomas Settle's performance of Galileo's inclined plane experiment, Drake implies that a clear view of Galileo's use of experiment is now emerging. Added emphasis was given to Drake's thesis that doubts concerning Galileo's use of experiment were largely unfounded, by James MacLachlan's realization of a Galilean experiment which was previously described as ‘imaginary’ by Koyré. The purpose of this paper is to suggest that, while it cannot be doubted that Galileo used experiment and precise measurement, his attitude to observation may well have been far more complex than Drake has supposed. My point of departure is James MacLachlan's remark that continuing disagreement over Galileo's use of experiment should lead to further examination of Galileo's experimental claims. I shall indicate that more than one view of Galileo's use of experiment may prove capable of explaining our present knowledge—a corollary of this being that alternative explanations may be proposed for the manuscripts recently published by Drake.

For the historian of thermodynamics, the outstanding events of the eighteenth century were the invention of the Newcomen atmospheric steam engine (1712), the patent of James Watt for a condenser separate from the engine's cylinder (1769), and Watt's further patent for the expansive use of steam (1782). These inventions, along with others concerned with hydraulic machinery, provided Sadi Carnot with the foundation on which he built, in 1824, the first fully general concept of a heat engine.

In the first half of the nineteenth century the largest and wealthiest ‘popular’ scientific establishment in London was the London Institution, founded by a group of prominent City men in 1805. During most of its early years this Institution had over 900 members; within a year of its foundation it had accumulated funds of £76,000, which dwarfed those possessed by any similar body in this period; by 1819 it had erected an imposing building in Finsbury Circus, a structure with a splendid library, a lecture theatre, and provision for laboratories, as well as meeting rooms. In that theatre eminent men of science and literature delivered lectures; by the 1840s William Robert Grove, then in the midst of his scientific career, was installed as ‘Professor of Experimental Philosophy in the London Institution’.