Watt’s indicator

While this interpretation of Watt and his work is coherent and its origins understandable, I contend that it fails to capture the eighteenth-century realities of Watt s work and how he understood steam and the engine improvements that eventually made his fortune and his name. The science of heat was certainly central to all that Watt did, but that science was chemical in nature. Strange as it may seem to us, for him the steam engine was at its heart a chemical device. Let s discuss in turn, and in more detail, the statue, the kettle and the indicator to see how they reflect the constructions of Watt in the nineteenth century. 

Others, notably Musson and Robinson, have stressed the scientific nature of Watt s work, often by indicating his reliance upon, or at least his close association with, Blacks researches on heat. Most recendy Margaret Jacob and Larry Stewart have endorsed this view on broader grounds.43 In much modern scholarship the boundaries between science/technology and between rhetoric/practice are not seen as being so readily drawn, if drawable at all. The contingent processes whereby such boundaries are constructed have become, for many, the object of study.44... 

Figure 1.10. Watt Statue, Watt Memorial Engineering and Navigation School, Greenock, showing Indicator in Watt s Right Hand. (Author s photo)...

For his part, Watt was more unconditionally welcoming and Priestley became part of the Watt family circle. They were to experiment together on numerous occasions. For example, Priestley collaborated with Watt and De Luc in experiments on heat, steam and evaporation in 1783, and there are indications that before and after this Priestley joined Watt at home in experimental work.61 They also routinely shared news of each others ideas and experiments. Very early on, Priesdey acknowledged the value of Watt s comments on his work in volume 2 of his Experiments and Observations on Natural Philosophy, and a brief letter from Watt, among others, commenting on aspects of the content of that work was included in the Appendix added after Priestley s arrival in Birmingham. Given that the preface of Experiments and Observations was dated 24 March 1781,... 

Watt s second paper, immediately following the first in the Transactions, was a short one.75 It gave advice about precautions to be taken by anyone repeating the experiments, and indicated some causes of variations in the results. Watt exhibited a typically firm diffidence about his own conclusions ... 

One more item in the list of Watt s contribution to the development of the steam-engine is too important to be passed without mention the indicator, which draws a diagram of the relation of the steam s pressure to its volume as the stroke proceeds, was first used by Boulton and Watt to measure the work done by their engines, and so to give a basis on which the charges levied from their customers were adjusted. 

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