Cet article vise à éclairer le contexte universitaire et éditorial qui favorisa la publication du Treatise on electricity and magnetism de James Clerk Maxwell afin de mieux cerner la nature de cette entreprise scientifique. Le projet fut formé en 1867 à l'occasion d'une réforme introduisant l'étude de l'électricité et du magnétisme dans l'enseignement délivré à Cambridge et s'inscrivait dans un mouvement plus vaste qui développait l'enseignement de ces disciplines dans les universités britanniques. L'étude des relations entre le projet de Maxwell (...) et d'autres ouvrages contemporains indique que le Treatise était en situation de devenir un ouvrage de référence en Grande-Bretagne. Ainsi, le livre de Maxwell était-il l'instrument d'une très ambitieuse tentative de transformation de l'électromagnétisme, indissociable de son contexte et conforme à sa fonction pédagogique. (shrink)

In June 1849 William Thomson wrote to Michael Faraday suggesting that the concept of a uniform magnetic field could be used to predict the motions of small magnetic and diamagnetic bodies. In his letter Thomson showed how Faraday's lines of magnetic force could represent the effect of the ‘conducting power’ for magnetic force of matter in the region of magnets. This was Thomson's extension to magnetism of an analogy between the mathematical descriptions of the distribution of static electricity and of (...) the diffusion of heat through uniform bodies. In 1850 Faraday published his first comprehensive theory of the magnetic properties of matter. He explained the behaviour of matter in the field by four assumptions: that matter has a specific disturbing effect on the normal distribution of lines of magnetic force; that this effect depends on its ability to conduct or transmit the magnetic action; and that material bodies tend to move so as to cause the least possible disturbance of the lines from their normal distribution. Faraday also assumed that diamagnetics transmit magnetic action less well than empty space, while paramagnetics transmit it more readily than space. This implied that space must have a specific conductivity between that of paramagnetic and diamagnetic materials. In order to preserve a distinction between matter and space Faraday defined ‘matter’ as either the source of action or as a conductor which is able to influence the lines of action; space was the absence of such powers. While space could conduct, it differed from matter in that it could neither originale lines of force nor influence their course and distribution. (shrink)

SummaryThe complex relation between molecular ideas and hydrodynamics in midnineteenth-century British science is considered. This relation is presented in the historical literature, almost invariably, in terms of a complete antithesis which signified an ontological commitment on behalf of British scientists to the idea that matter was essentially continuous. However, the analysis will reveal that molecular ideas were scattered within the main body of hydrodynamics and that molecular discourse was intersecting hydrodynamical discussions at specific points. Questions of resistance and complex fluid (...) phenomena were inviting various molecular conceptualizations of fluid matter, although these never took the form of a complete mathematical theory. (shrink)

Though P. G. Tait was in a seemingly perfect position to teach both William Thomson's thermodynamics and James Clerk Maxwell's electromagnetic theory of light, he did not. Tait probably first encountered the new thermodynamics in the 1850s at Queen's College, Belfast, and presented the ideas in his inaugural lecture at Edinburgh in 1860, soon making energy theory the centre-piece of his course there. The comprehensiveness of energy theory plus Thomson's opposition to Maxwell's electromagnetic theory evidently combined in causing Tait to (...) de-emphasize Maxwell's theory. Ironically, Tait, the loyal Scot, thus inadvertently contributed to what might be termed the Anglicization of Scottish natural philosophy. (shrink)

Based largely on unpublished manuscript material from the Kelvin papers, and especially on a series of letters exchanged in 1867 between Fleeming Jenkin and William Thomson , this paper aims to examine the background and content of the Thomson-Jenkin speculations on the nature of matter. The letters formed an interlude in a long collaboration over electrical patents and raise the fundamental question of whether these speculations, involving the construction of a variety of conceptual models, derive primarily from older traditions of (...) speculative matter theory, or from contemporary problems within natural philosophy qua physics. The correspondence also provided the immediate background to Jenkin's North British review article of 1868 on ‘Lucretius and the atomic theory’. (shrink)