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.

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.

Compared with other scientists of the nineteenth century, the German chemist Justus von Liebig (1803–73) was a complex figure. In part, this was because Liebig established such broad borders for his science. Chemical methods, popular and professional publications about chemistry, technological applications, promoting the car and even politics – all were central concerns stemming from Liebig's notion of chemistry as the central science.

When Liebig discovered John Stuart Mill's Logic, a work on the philosophy of science, it struck a deep chord within him. Mill's high praise for Liebig's chemistry certainly provided Liebig with a means to promote his own reputation. In addition, Mill's Logic presented science as a central method for the general reform of society, a goal Liebig was himself struggling to define in the early 1840s. In the scientific method, Mill discovered a ‘rule by the elite’, which he could never find nor justify in his political philosophy. This was a rule that greatly appealed to Liebig, and he set out to ensure that Mill's work was translated and published in German. Though many details of this transaction are known, this paper seeks to investigate the relationship between Liebig and Mill's book, and the significance of this relationship for understanding Liebig's role as a gatekeeper and inter-relations between science and politics.

The bitterness and protracted character of the biometrician–Mendelian debate has long aroused the interest of historians of biology. In this paper, we focus on another and much less discussed facet of the controversy: competing interpretations of the inheritance of mental defect. Today, the views of the early Mendelians, such as Charles B. Davenport and Henry H. Goddard, are universally seen to be mistaken. Some historians assume that the Mendelians' errors were exposed by advances in the science of genetics. Others believe that their mistakes could have been identified by contemporaries. Neither interpretation takes account of the fact that the lapses for which the Mendelian eugenicists are now notorious were, in fact, mostly identified at the time by the biometricians David Heron and Karl Pearson. In this paper we ask why their objections had so little impact. We think the answer illustrates an important general point about the social prerequisites for effective scientific critique.

Stargazing Knight Errant, beware of the day When the Hottentots catch thee observing away! Be sure they will pluck thy eyes out of their sockets To prevent thee from stuffing the stars in thy pockets

If Herschel should find a new star at the Cape, His perils no longer would pain us He will salt the star's tail to prevent its escape And call it ‘The Hottentot Venus’.

Astronomy has long been recognized as a tool of empire. Its service to navigation and geography have made it indispensable to European expansion. Britain in particular excelled at this brand of control; each day when the sun set on the British empire, its telescopes continued to enhance imperial power.

While the above claims are no longer controversial, we have hardly begun to understand the extent to which imperialism subsequently changed the nature of the physical sciences.

A Metaphysical Subject © Martha Fleming