The magnetic circuit model acts as a unifying principle in descriptive magnetostatics, and as an approximate computational aid in electrical machine design. It was the subject of repeated rediscoveries through the period 1855 to 1886, taking different forms and being provided with different justifications but all motivated by the mathematical difficulty of existing magnetic theory. The process culminated in several competitively-slanted announcements of the principle made during 1884 to 1886, arising in connection with the already comparatively efficient designs of contemporary dynamos which made its application plausible. The preferred conceptual imagery, of induction flow against a ‘resistance’, originated in the magnetic theories of Faraday, though these underwent considerable changes before adoption.

The periodical History of Science opened auspiciously in 1962 with an article by L. Pearce Williams on ‘The physical sciences in the first half of the nineteenth century: problems and sources’. He criticized the nearly exclusive reliance on printed sources then quite common in studies of Victorian science, concluded that much remained to be discovered and closed his paper with these words: What papers exist in private hands can only be guessed. I know of a trunk in an attic containing unpublished letters from Darwin, Huxley, Kolbe, Pasteur and a host of others. They are, unfortunately, not available to the scholar and there must be hundreds, if not thousands, of such boxes scattered through America and Europe. As they are discovered, catalogued and made available to scholars, the shape of nineteenth-century science will gradually lose its blurred outlines and the origins of modern science will become clear.

It can certainly be said that history of science has experienced a large growth in recent decades in Spain. This has occurred despite the generic term ‘history of science’ covering activities of a very varied nature and lacking an intimate relation between each other, in research as well as instruction. At present the number of publications which could fit into the frame of this branch of learning has increased remarkably and commercial publishing houses have opened their editorial lists to the publication of classics as well as to monographs on the history of science. Moreover, new specialized journals on these subjects have become popular and have joined the small number of journals which already had a certain tradition. The number of participants in the periodical congresses of the Sociedad Española de Historia de las Ciencias y de las Técnicas [SEHCYT] has risen and the number of congresses and symposia that have been held in Spain and have assembled Spanish as well as foreign historians has also increased. As another recent promising detail, we could quote the presence of history of science in the curricula of Spanish university programmes, a presence that tends to increase progressively.