This paper focuses on the defection of nuclear physicist Bruno Pontecorvo from Britain to the USSR in 1950 in an attempt to understand how government and intelligence services assess threats deriving from the unwanted spread of secret scientific information. It questions whether contingent agendas play a role in these assessments, as new evidence suggests that this is exactly what happened in the Pontecorvo case. British diplomatic personnel involved in negotiations with their US counterparts considered playing down the case. Meanwhile, the press decided to play it up, claiming that Pontecorvo was an atom spy. Finally, the British secret services had evidence showing that this was a fabrication, but they did not disclose it. If all these manipulations served various purposes, then they certainly were not aimed at assessing if there was a threat and what this threat really was.

The Marxist history of science has played an enormous role in the development of the history of science. Whether through the appreciation of its insights or the construction of a political fortress to prevent infusion, its presence is felt. From 1931 the work of Marxists played an integral part in the international development of the history of science, though rarely have the connections between them or their own biographies been explored. These networks convey a distinct history, alongside political, methodological and personal implications, impressing on us a greater understanding of the possibilities that were present and were lost in the most turbulent of decades. Two of the most notable were Boris Hessen, a founder of Marxist history of science, and J. G. Crowther, one of its most prolific exponents. My examination explores aspects of the dialogue between these controversial figures, starting with brief biographical sketches. Their lives became briefly entwined following the Second International Congress of the History of Science and Technology in 1931, demonstrated with reference to the meeting and the correspondence between them until Hessen's death. In doing so, some new facts and old controversies surface, though most importantly the nature of the correspondence carries implications for the Marxist history of science and for the wider movement of which it is part. The Russian delegation to the congress declared that science was at a crossroads. The history of science was at a similar crossroads in the 1930s.

Between 1867 and 1869 Michel Chasles presented a series of manuscripts to the Académie des sciences, which suggested that Isaac Newton's claims to original discovery were unfounded. It quickly became apparent to the majority of the academicians that the manuscripts were forgeries, but Chasles was repeatedly allowed to state his case. This essay focuses on the responses to the affair from four British men of science: David Brewster, Augustus De Morgan, Robert Grant and Thomas Archer Hirst. It asks why they felt it necessary to add their voices to this debate and examines their various strategies for refuting Chasles's evidence.

Joseph Dawson is known mainly as one of the founders of Low Moor Ironworks, near Bradford (Yorkshire). But he also had wide interests in science. Local museum collections illustrate several aspects of his work in chemistry and mineralogy. His mineral collection is particularly important because it is accompanied by a rare early catalogue in Dawson's hand. This shows how he arranged his 2206 mineral specimens according to Thomas Thomson's essentially Wernerian classification. Dawson's comments about minerals as well as about iron furnaces demonstrate a view of science in which chemistry was fundamental. Moreover, his contacts with other iron-masters and leading industrialists, as well as with mineralogists and Nonconformist ministers, show him active within several networks through which scientific ideas, attitudes and practices were disseminated.

In the beginning, there was Dava Sobel and Longitude: The True Story of a Lone Genius Who Solved the Greatest Scientific Problem of His Time (1998). Others followed, in a veritable flood which D. P. Miller recently dubbed the ‘Sobel Effect’. Academic historians of science have been concerned by this flood, partly because people other than them are (presumably) making money out of ‘their’ subject, but also because of the ways it might affect the public perception of the history of science. Like the scientists they study, historians fear that popularizers will distort in the process of simplifying. But, knowing how difficult it has been for scientists to control the popularization of their subject, historians may not expect a great deal more success.