It has been a singular privilege to preside over the BSHS as it celebrates its fiftieth anniversary. As we share our festivities with the British Association annual meeting at Leeds, I am doubly honoured to be giving this address. A fiftieth anniversary is a sentimental occasion. It is a moment when we can express our gratitude to our many friends and forebears who by their dedication have enabled the Society to grow and flourish. That so many of those friends should be with us to share in our celebration is a source of delight to us all. To our past presidents, former editors, officers and councillors, I extend the warmest welcome. And to our visitors and guests from overseas, I should like to say how much we value your presence and contribution to this conference.

Is there not, then, an incongruous note in my title – a hint of foreboding perhaps? If tempted to speculate on its source one might have wondered whether it is in those rumours we sometimes hear that the end of science is nigh. When we can almost clone humans and almost explain the moment of creation, what is there left? Might the end of science not spell the end of its history? A moment's reflection suggests that this cannot be. After all, the question why science should have come to an end when it did would still keep historians in business. And the more intriguing question of why the end of science has been proclaimed at the end of each of the last four centuries would keep us in business even longer!

It was well said by Clerk Maxwell: ‘For the sake of persons of different types of mind scientific truth should be presented in different forms, and should be regarded as equally scientific whether it appears in the robust form and colouring of a physical illustration, or in the tenuity and paleness of a symbolical expression.’

From N. V. Sidgwick's Presidential Address to the Chemical Society, London, 1937

During the years between 1930 and 1950, chemistry underwent a transformation that affected both research and education. New subdisciplines like chemical physics and physical organic chemistry emerged, encouraging an influx of ideas and experimental techniques from physics. X-ray crystallography and other spectroscopic methods became indispensable for determining structures of atoms, molecules and crystals; such chemical concepts as valence and bond were refined within a new explanatory framework based on principles of physics; and the study of reaction mechanisms and rates became closely intertwined with that of structures and properties of chemical compounds. In conjunction with these changes, introductory chemical textbooks began to shift their emphasis from thermodynamic equations and solution theories to three-dimensional arrangements of atoms in molecules and types of chemical bonds. There is no doubt that the most important impetus behind this transformation was the development of quantum mechanics in the mid-1920s, and the most prominent among those who applied it to chemistry was Linus Pauling. And in Pauling's view, ‘the principal contribution of quantum mechanics to chemistry’ was the concept of resonance.

The entry of resonance into chemistry, or the reception of the theory of resonance in the chemical community, has drawn considerable attention from historians of science. In particular, they have noted Pauling's flamboyant yet effective style of exposition, which became a factor in the early popularity of the resonance theory in comparison to the molecular orbital theory, another way of applying quantum mechanics to chemical problems. To be sure, the non-mathematical presentation of the resonance theory by Pauling and his collaborator, George Wheland, helped to facilitate the reception; but this presentation was vulnerable to the confusion that arose among chemists owing to the similarity between resonance and tautomerism, or between foreign and indigenous concepts. The reception occurred at the expense of serious misunderstandings about resonance. This paper investigates the ways in which Pauling and Wheland taught, and taught about, the theory of resonance, especially their ways of coping with the difficulties of translating a quantum-mechanical concept into chemical language. Their different strategies for teaching resonance theory deserve a thorough examination, not only because the strategies had to do with their solutions of the philosophical question whether resonance is a real phenomenon or not, and whether the theory of resonance is a chemical theory or a mathematical method of approximation, but also because this examination will illuminate the role of chemical translators in the transmission of knowledge across disciplinary boundaries.

For over half a century, from 1924 to 1986, the Electrical Association for Women (EAW) worked to modernize the British home by bringing the blessings of labour-saving appliances to the aid of British women. Adopting a strategy of facilitation, the EAW sought, on the one hand, to educate women about electricity and its advantages in the home, encourage them to demand greater access to that electricity and keep them abreast of new developments in appliances and the infrastructure (from a national grid to sufficient outlets) necessary for enjoying them. On the other hand, the organization sought to discover the real needs and desires of the women themselves, and to bring this forcibly to the attention of the electrical industry in Great Britain ; to make the ‘women's point of view’, as it was called, a factor in the production, distribution and application of electricity in the home.

Although the very masculine electrical industry was a decisive part of both the EAW's context, and of its financial and advisory structure, the group proudly insisted that it was a women's organization in which women addressed other women about women's concerns and well-being. In its early years, the excitement of women coming together in a modern cause was palpable, but as the leadership aged and electricity turned from modern vision to commonplace reality, the almost religious zeal and pace of activities began to falter. A late-hour attempt to highlight nuclear power plants as evidence of a renewed and equally exciting modern moment fell short, and in 1986 the EAW quietly dissolved itself, the casualty of large social changes, some of which it had proudly helped to bring about.

In the late spring of 1947, the experimental physicist P. M. S. Blackett succumbed to the temptations of theory. At this time, Blackett (1897–1974) was fifty years old. He was a veteran of the Cavendish tradition in particle physics and he was on his way to an unshared award of the 1948 Nobel Prize for his experimental researches in nuclear physics and cosmic-ray physics. His photographs of cloud-chamber tracks of alpha particles, protons, electrons and positrons were well known to practitioners of particle physics, even as they now grace the pages of physics textbooks.

Blackett's turn toward theory in 1947 involved some risk for a well-established experimental physicist. The 3 May 1947 issue of Nature carried an announcement of his forthcoming lecture at the Royal Society:

Professor P. M. S. Blackett, Langworthy Professor of Physics in the University of Manchester, will deliver a lecture on ‘The Magnetic Field of Massive Rotating Bodies’ at a meeting of the Royal Society on May 15, at 4:30 p.m.

Blackett circulated a preliminary draft of his paper among colleagues in several different fields, including the geophysicist Sydney Chapman and the astrophysicist Harry Plaskett.

On Wednesday 27 April 1898, Dr Luigi [Louis] Westenra Sambon (1865–1931) addressed the Royal Geographical Society in London on a topic of much interest to the Victorian public. An Anglo-French medical graduate of the University of Naples, a Fellow of the London Zoological Society and a recent visitor to Central Africa, he was well equipped to tackle the subject of the ‘Acclimatization of Europeans in Tropical Lands’. The ‘problem of tropical colonization’, he began, ‘is one of the most important and pressing with which European states have to deal. Civilization has favoured unlimited multiplication, and thereby intensified that struggle for existence the limitation of which seemed to be its very object…I know full well that the question of emigration is beset with a variety of moral, social, political, and economic difficulties; but it is the law of nature, and civilization has no better remedy for the evils caused by overcrowding.’

Even from these introductory remarks, it is already plain that Sambon's project was a compound product of medical diagnosis, colonial imperative, Darwinian demography and moral evaluation. And it is the rhetorical zone roughly marked out by this quadrilateral of disease, empire, struggle and virtue that I want to explore here. First, however, it will be instructive to return to that afternoon a century ago and spend a little more time listening in on the deliberations.