On 30 April, 1897, J. J. Thomson announced the results of his previous four months' experiments on cathode rays. The rays, he suggested, were negatively charged subatomic particles. He called the particles ‘corpuscles’. They have since been re-named ‘electrons’ and Thomson has been hailed as their ‘discoverer’. Contrary to the accounts of most later writers, I show that this discovery was not the outcome of a concern with the nature of cathode rays which had occupied Thomson since 1881 and had shaped the course of his experiments during the period 1881–1897. An examination of his work shows that he paid scant attention to cathode rays until late 1896.

So much of the history of science has been written from the point of view of the scientist or the proto-scientist that it may be salutary for the modern reader occasionally to consider how science and its early practitioners were viewed from the outside. We must not be too surprised if a pioneering activity performed by controversial agents was misunderstood or misrepresented and if what emerges is, therefore, sometimes less of a portrait than a caricature. We are concerned here much less with what natural philosophers actually did than what they were thought to have done, or what they were thought to stand for. The image is sometimes more influential than the reality. Considering that the period to be studied is one of major political and social unrest and that the principal spokesman, Edmund Burke (1729–1797), had made his reputation mainly in the arena of parliamentary politics, we can anticipate rather more polemic than dispassionate argument. In the formation of public opinion a colourful exaggeration or even an occasional sneer are often more effective than the objective exposition of a case. The spectacles through which Burke looked at his world sometimes magnified and often distorted, but they produced a view of knowledge and society shared by many of his contemporaries and of considerable subsequent influence.

André-Marie Ampère's contributions to electrodynamics came at a late stage in an unconventional career. In 1820, he had reached the age of forty-five and had not as yet done any systematic research in physics. As a member of the mathematics section of the Académie des Sciences, his only significant contributions to the physical sciences had been some constructive criticisms of Fresnel's wave theory of light and three memoirs on chemical classification and gas theory. Meanwhile, his longstanding interests in metaphysics and epistemology had resulted in pointed methodological and philosophical attitudes which both motivated and structured his subsequent work in electrodynamics. Not surprisingly, events during the first few months of Ampère's research included many unplanned and unexpected encounters as this wildly enthusiastic theoretician grappled for the first time with the recalcitrant complexity of actual experimentation in an uncharted new domain.

After Jacobus Henricus van't Hoff had passed away on 1 March 1911, his pupil Charles Marinus van Deventer (1860–1931) wrote a very personal ‘in memoriam’ in the Dutch literary periodical De Gids, pointing out that van't Hoff had merely been interested in scientific facts, not in the people discovering these facts. Van't Hoff considered the study of the history of chemistry, although by no means uncongenial, a matter of little importance. He once even said: ‘To me historical research appears to be appropriate for a chemist in the decline of life, when he no longer creates professional ideas, and when the laboratory has become a burden to him’. Although van Deventer had studied physical chemistry at van't Hoff's Amsterdam laboratory and had been his assistant from 1885 until 1893, he disagreed with this verdict. Van Deventer was not only a capable physical chemist, he was also an active member of the Tachtigers, a circle of Dutch poets who around 1880 brought about a renewal in Dutch literature. He took a special interest in Greek philosophy. He did not graduate with van't Hoff, but with his colleague Jan Willem Gunning (1827–1900). His thesis was not based on physical-chemical, but on historical research: Schetsen uit de Geschiedenis van de Scheikunde (‘Sketches from the history of chemistry’; 13 December 1884). From 1922 to 1923 he lectured on the history of chemistry at Utrecht University. His fascinating lectures were published as Grepen uit de Historie der Chemie (‘Choices from the history of chemistry’; 1924). This work reveals his particular interest in the development of chemical concepts.