The X Club formed in 1864, consisting of nine men who met once a month in London to dine and enjoy conversation on scientific subjects free from the restraints of religious dogmatism. It grew out of a looser network of friends and allies who found common cause in the theories of Charles Darwin and a desire for intellectual freedom. They are usually characterized as the most influential scientific body of the nineteenth century, responsible for carving out a significant place for science within public culture and wielding their power to further the agendas of scientific naturalism, secularization and professionalization. Barton does not set out to entirely dismantle previous scholarship, but the book nevertheless departs from more sweeping treatments of the X Club that have tended to take the views of its better-known members as representative of the whole. Rather, Barton brings together various threads of historiography and submits them to reassessment through the lens of a ‘deliberately unheroic’ (p. 8) group biography.

Insofar as it is possible for nine men to be ‘diverse’, the backgrounds and scientific interests of the X Club's members were sufficiently varied that their individual biographies demonstrate the multifarious routes to scientific achievement in mid-nineteenth-century Britain. Barton divides the nine members of the X Club into four categories – or ‘cultures’ – broadly according to their social background. At the one end of the class spectrum, Edward Frankland, John Tyndall and Thomas Archer Hirst were artisans who sought self-improvement through science. In the case of Hirst, his Yorkshire accent was a source of social embarrassment and an ineradicable trace of his origins. Herbert Spencer and Thomas Henry Huxley, meanwhile, came from the tradition of ‘radical provincial dissenting science’, but the latter soon adopted metropolitan values to further his scientific ambition. William Spottiswoode, junior partner in the Eyre & Spottiswoode printing firm, was the only member of the X Club with an Oxbridge education. George Busk, Joseph Hooker and John Lubbock represented gentlemanly metropolitan science. Lubbock owed much of his scientific status to inherited wealth and title, while Hooker succeeded his father as director of the Royal Botanic Gardens, providing him with a relatively easy entry into the scientific coteries of London. This range of experience allows Barton to achieve both breadth and depth in her account of mid- to late nineteenth-century scientific careers, and consistently demonstrates the role of social status in shaping the careers of her subjects. The narrative of professionalization in science during the second half of the nineteenth century has been so thoroughly critiqued in the last few decades (not least by Barton herself) that it is no longer necessary to launch further attacks, but rather to continue the more constructive process of determining the aims and strategies adopted by actors in shaping their scientific identities. As in her earlier work on this subject, Barton plays close attention to the language of self-description and carefully avoids the use of problematic terms such ‘amateur’ and ‘professional’. More precise vocabulary is required in negotiating this thorny historiographical ground, and she suggests alternatives such as ‘salary-dependent’ and ‘specialist’ that more accurately express the subtle distinctions among these men and their peers.

While the likes of Huxley, Tyndall and Hooker have been given more detailed individual treatment by scholars, other members of the X Club remain relatively obscure. It is therefore a strength of the group biography that less well-known figures are given greater attention and the more famous members reintegrated into the collective context. George Busk emerges from Barton's account as a far more proactive figure than hitherto recognized, though he must remain necessarily underrepresented due to a lack of surviving material. Also included are an extensive supporting cast of family members and collaborators, showing the degree to which the X Club relied on a far wider support network. As is perhaps to be expected in a book focusing on the predominantly masculine world of nineteenth-century gentlemen's clubs and scientific societies, women do not feature in great numbers, but Barton nevertheless gives a sensitive (if brief) account of the X wives as a vital extension of the core group. Looking beyond the more outspoken X Club members, Barton gains fresh insight into well-worn topics. In her treatment of scientific naturalism, the philosophical position most closely associated with the X Club, Barton argues that the ‘silent majority’ (those other than Huxley, Spencer and Tyndall) have been neglected by historians, leading to a simplified definition of their theoretical standpoint. Rather than a fixed doctrine, she argues, the often idiosyncratic views of these individuals are better understood through a looser approach that seeks to identify the shared assumptions and arguments that tied them together.

This book was clearly a deeply personal project for Barton, who admits she has ‘lived with these nine men for decades’ (p. 1). She has set a significant benchmark in scholarship on the X Club that will no doubt remain the chief reference work on the subject for some time.