Reviewing these two books together has been a delight. Both authors visited the Science Museum, London, during the preparatory work for the 2010 exhibition James Watt and Our World, the last exhibition I worked on before retiring in 2012. Werrett's concern with thrift, a word with many more meanings than I had fully appreciated, reminded me that James Watt referred to his notebooks of expenditure as ‘waste books’. Miller was debunking myths about steam kettles, alongside a deeper concern to clarify Watt's own ideas about the ‘chemistry of heat’, and how far polymath Watt engaged with his material world both as a well-connected autodidact philosopher and as an engineer.

Professor David Miller, emeritus professor of history of science at the University of New South Wales, Sydney, has been interested in his subject for more than twenty years. Dr Simon Werrett is senior lecturer in history at UCL's Department of Science and Technology Studies, and has pursued this topic since 2013, following earlier work on the history of fireworks. Both have consulted a huge amount of material. For Miller, this has included archives throughout Britain, as Watt's work on steam engines and the promotional efforts of his family and colleagues (‘Team Watt’, as Miller has it) has resulted in copious significant holdings from Cornwall to Glasgow. Miller also credits more recent appraisals; the late Richard Hills’s three-volume work of 2002–2006 was followed by studies by Ben Marsden, Ben Russell, Maxine Berg, Celina Fox, Margaret Jacobs, Peter Jones and Ursula Klein. Werrett's reading included scouring early modern science writings in Britain for mentions of domestic context and applications of readily available domestic utensils to what we would now recognize as scientific purposes, and the equivalent period's publications of household oeconomy, for traces of science-like practice.

Miller opens with an imagined tale of Watt receiving the news of the death of his first wife. This was a pivotal moment in Watt's career, facilitating the move from Glasgow (where he ran several businesses from college premises obtained through family connections and contacts) to Birmingham, where one of the larger myths later held that his business partner Matthew Boulton was the entrepreneur, and Watt the brilliant inventor. Not all the chapters run consecutively; Miller investigates different aspects of Watt's life, influences, family and business practices, with consideration not only of Watt's own thinking, but also of the ways that the business was supported and promoted by collaborators who may not have been clearly acknowledged at the time. He also considers Watt's approach to material success, how he accrued and nurtured his own fame, and the posthumous positioning as a national icon, including the unintended consequence of climate change from the industrialization he enabled.

Werrett begins by reminding his readers that our present visions of the future tend more to dystopia than to unlimited space travel, and there is a growth in enthusiasm for repairs and mending along with recycling. He suggests that this is not just a rediscovery of environmental counterculture from the 1900s and 1970s, but ‘a re-recognition of thrifty practices that have been going on for centuries’; his present interest is in early modern approaches to experimenting and exchanging medical, culinary and chymical knowledge in the households of the protagonists (p. 2). Things were understood to be open-ended and multifunctional, stored, used and maintained carefully to prolong active utility, and worthy of exchange and transfer used or second-hand. Studying nature included making use of both the home and its contents – furniture, pokers, gunbarrels and even socks.

Miller positions himself as considering Watt as an ‘improver’ in the Scottish Presbyterian tradition. The first steam patent was to lessen the consumption of steam and fuel in fire engines; later development in expansive working included shutting steam off before the engine's piston had reached the end of the cylinder, giving only half the possible power, but using only a quarter of the fuel. Watt's understanding of his inventions was underpinned by investigations of the nature of heat, gases or ‘airs’ and water, and other debates in contemporary chemical practice, Miller being careful not to apply more modern concepts such as thermodynamics in considering Watt's experimental work. Miller was also concerned to correct an overdrawing of the myth of the ‘lone genius’, bringing many of Watt's collaborators into better focus.

Werrett also drew on previously underappreciated ancillary workers in early modern science endeavour, responsible for the cleaning, maintenance, repairs, recycling and repurposing of everyday materials and equipment. He also considered how this, and knowledge, could be passed on, second-hand, by various exchange methods, and latterly auctions, making the most of what is available. He saliently noted that this did not stop with the development of specialized instrumentation, nor with dedicated laboratory spaces for scientific activity. Unravelling a different understanding of early modern multipurposing helps to make sense of modern trends and to re-evaluate alternative futures.

Miller's work could be seen as an end-of-project concise summary of decades of study; Werrett's is one step in a longer journey which I gather may see him extend his area of interest beyond Britain. Physically, the books are similar in size, but Miller's has 322 text pages to Werrett's 200, although their bibliographies and endnotes occupy similar numbers of pages. The discrepancy arises from the regrettably small font used by the Pittsburgh Press for Miller's book. One irresistible story connecting Watt with domestic oeconomy in the Werrett sense was the observation that the first model of the separate condenser, the mechanism that kick-started the Industrial Revolution, used an enema syringe. I had forgotten this; Werrett did not. I salute the determination and hard work of both authors; obsession, when it results in works like these, is wonderful.