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Abstracts

Neil Todd:
Rutherford and the 1912 Extension to the Physical Laboratories of the University of Manchester.
On the evening of 1 March 1912 a conversazione directed by Arthur Schuster was held in the Physical Laboratories of the University of Manchester to mark the opening of the new extensions. It seems appropriate then to mark the centenary of the 1912 extension with a discussion on its significance for Rutherford‘s science at Manchester, especially since our meeting will be held in March 2012 the old 1912 Physical Lecture Theatre. In addition to the fact that there was considerable overcrowding in the old 1900 Building, in part due to the massive expansion in the number of researchers in the Rutherford school, an important argument for the new extension was that it would create an environment free from the radioactive contamination which was by then widespread throughout the old Laboratory. The contamination free physics rooms enabled Rutherford to develop his interest in gamma and beta-ray spectroscopy, which required long exposure times, and which became a major thrust of his work at Manchester before the outbreak of war in 1914.

Brian Cathcart:
Rutherford's resonance: responses to the discoveries of 1911 and 1932.
The unveiling of the nuclear atom and the first artificial disintegration of the nucleus, events divided by 21 years, represent two great high points in the astonishing career of Ernest Rutherford and yet the responses, both scholarly and among the press and public, could hardly have been more different.

The former met a sullen silence while the latter prompted what today might be called a global media frenzy, complete with sensational speculation. This talk, by a historian who is also a journalist, considers possible explanations for the contrast, looking at the characters of the two events themselves, and at changes in the public understanding of science, in the press and in the great man himself.

Geoffrey Constable:
The apparatus used for the discovery of the neutron.
Following a series of famous experiments, Dr Chadwick announced the discovery of the neutron in February 1932 via a letter to Nature. The scientific arguments supporting this discovery were described here and, more fully, in the subsequent Royal Society paper, and are well known. These documents provided an outline of Chadwick's apparatus sufficient for scientific purposes. However, the details of this apparatus are sketchy and there are no detailed drawings or records in the Cavendish archives or elsewhere in the public domain. Hence there are gaps in our knowledge, particularly as to how and where this apparatus — which was innovative — was constructed, proven and refined. The object of this paper is to fill in some of these gaps.

Dr Jack Constable — the father of the present writer — was a research student at the Cavendish Laboratory from 1928 to 1931. Under the supervision of Chadwick, he contributed to the design of a novel 'valve counter' plus associated devices that collectively formed a system for detecting and automatically recording radiation. He then undertook the construction of this system, plus its proving and subsequent development. His PhD studies concluded with a series of experiments that involved bombarding various elements with alpha particles from a polonium source in order to measure the energy levels of the emerging radiation.

Such experiments were similar in function to those undertaken a few months later by Chadwick (but had a different objective) and it is clear from contemporary papers that the apparatus used in both cases was one and the same. A recent examination of family papers and other records, some photographic, has yielded fresh information concerning the apparatus used by Chadwick. In particular, light is shed on a (then) new experimental technique, an unusual approach to constructing scientific apparatus, a raft of detailed refinement that led to the remarkable sensitivity and resolution that was achieved, and a little known experimental result that could have led (but didn't) to the earlier discovery of the neutron.

Page last updated 18 March 2012