Allan Chapman

A study of the accuracy of scale graduations on a group of European astrolabes

Summary Precision measurements have been made of the scales on a group of European astrolabes manufactured between c. 1450 and 1659. Little is known from documentary sources of the construction and scale-dividing methods used by late-medieval craftsmen. The measurements of the present group of twenty-four scales have been analysed statistically, so that the parameters of accuracy expected of them can be deduced. Scribing marks and other features give clear indications of how the scales were constructed.

An occupation for an independent gentleman: Astronomy in the life of John Herschel

Abstract Sir John Frederick William Herschel occupies a pivotal position in the history of British astronomy (1). He formed the living link between two styles or traditions of science by being the last major specimen of one breed, and the inspiration and intellectual role model for the generation that would follow. For John Herschel was perhaps the last significant figure to devote himself wholly and full-time to fundamental research in astronomy and its related sciences on the strength of a private fortune. And while the stature that he enjoyed did much to stimulate the concept of the ‘professional’ astronomer in Britain, so many of these men of the rising generation who admired his thorough-going dedication to science were themselves more obviously professional in the respect that they earned their livings through academic science. One sees in him, therefore, an eclectic blend of attitudes towards what science was, how it should be pursued, and how it should be paid for.

Jeremiah Horrocks, William Crabtree, and the Lancashire observations of the transit of Venus of 1639

When Jeremiah Horrocks correctly predicted, and with his friend William Crabtree observed, the Venus transit of 24 November 1639, these two men became more than the first astronomers in history to witness a rare celestial phenomenon. For Horrockss and Crabtrees achievement constituted in may ways the first major astronomical discovery to be made in Renaissance England. It is also clear from their writings, moreover, that the two men, working in the isolation of rural Lancashire and well away from London or the universities, were fully conversant with contemporary discoveries made in continental Europe by Tycho Brahe, Galileo, Kepler, Gassendi, and others. In many ways, therefore, their work begs more questions than can easily be answered, such as why the rural North-West produced not only Horrocks and Crabtree, but other contemporary astronomers such as the Lancastrians Charles Towneley, Jeremy Shakerley, and their Yorkshire friend William Gascoigne. Yet in addition to whatever regional circumstances might have been present, and how easy it might have been for an educated rural Lancastrian to be fully informed about what astronomers in Paris, Prague, or Florence were doing, what cannot be denied is the outstanding originality of their wider achievement. For Jeremiah Horrocks in particular was a physical scientist of genius. His correct determination of the elliptical shape of the lunar orbit by 1638 when he was about 20 and his wider work on planetary dynamics place him amongst the most creative researchers of the seventeenth century. Central to Horrockss and Crabtrees achievement was Crabtrees realisation by 1636 that contemporary published astronomical tables were unreliable, and that if one wanted to do serious work in understanding the heavens, then one had to observe and measure them for oneself, and learn to draw original conclusions. To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The design and accuracy of some observatory instruments of the seventeenth century

Summary The graduated arcs of some seventeenth and early eighteenth-century observatory instruments have been examined in order to estimate the accuracy of the angular divisions. In addition, the design of the frameworks supporting the graduated arcs has been studied from existing instruments and from contemporary engravings. The analysis attempts to assess the skills of the craftsman rather than the perspicacity of the astronomer.

Pure Research and Practical Teaching: The Astronomical Career of James Bradley, 1693-1762

When James Bradley was born 300 years ago, astronomy was by far the most advanced of the sciences, and set standards of both theory and practice which it was felt that natural history, chemistry and medicine should somehow emulate. Bradley, moreover, was born into the immediate post-Newtonian generation of the science, when astronomers were working out the consequences of the inverse-square law to investigate the orbits of the Moon and comets, determine the precise shape of the globe, and measure its mass. Principia, after all, contained several manifestos about how physics should work, and for more than a century after its publication in 1687, scientists were devising courses of observations that were intended to detect Newtonian criteria. Most of James Bradley’s professional life was spent in detecting and quantifying motions that were consequences of gravitation. James Bradley was born at Sherborne, Gloucestershire, in March 1693, though as the Parish records do not survive, we do not know upon which day in March. Popular tradition, however, ascribes it to the 23rd day of that month.1 His father, William Bradley, was a man of modest means, though his mother, formerly Jane Pound, was sister of Dr James Pound, Rector of Wanstead, Essex, who was a leading amateur astronomer. Dr Pound recognized his nephew’s intellectual abilities, encouraged his interests in astronomy, and after James’s education at Northleach Grammar School, was probably instrumental in getting him to Balliol College, Oxford.2

Tycho brahe in china: the Jesuit mission to Peking and the iconography of European instrument-making processes

Summary In the late 1660s, Ferdinand Verbiest, a Flemish Jesuit missionary in Peking, was instructed to re-equip the Imperial Observatory. The new instruments which he caused to be built were modelled neither upon contemporary European prototypes, nor those of traditional Chinese astronomy, but on the pieces in Tycho Brahes Mechanica, of eighty years before. The Chinese instruments were lavishly illustrated, moreover, in 105 woodcuts that contained detailed representations of their processes of construction. It is argued that these illustrations not only give us valuable insights into what the technical Jesuits did in Peking, but show how sixteenth- and seventeenth-century European craftsmen constructed their instruments, for while the location was Oriental, the technology was Western. They can also give important insights into how Tychos prototypes had been built, and provide us with useful information regarding European instrument-making technology.

Conclusion: A Career in Retrospect

Would Mary Somerville have achieved more, and gone on to make major scientific discoveries, had she been able to go to university, hold down a job, and become the Professorial Director of some research institute? Richard Anthony Proctor, her Royal Astronomical Society obituarist in 1872, lamented that the social proprieties of her day had made it impossible for Mary to really achieve her potential as a planetary dynamicist, while Dr. Mary Bruck, in her excellent and perceptive biographical article, styled her a ‘mathematician and astronomer of underused talents.

The Domain of Nature: Astronomy, Optics and Geology

While there were major differences of national style, funding and career paths between the scientific communities of England, France and the other Continental countries, the scientists themselves shared the same broad intellectual concerns. It is true that while some countries had their especial distinctions—France for pure mathematics and physiology, Germany for organic chemistry and manufacturing optics, and England for experimental physics and observational astronomy—all of these scientists acknowledged the same concepts of nature, and recognised parallel standards of excellence. In her writings between 1825 and 1869, Mary Somerville was to explore this world of ideas, showing herself to be an ingenious experimentalist on the one hand, and a brilliant surveyor, interpreter and high-level communicator of contemporary science on the other.

Mary Somerville and Her Influence

On 28 July 1897, Miss Florence Taylor, a young woman who was probably a school teacher by profession, delivered a lecture to the newly refounded Leeds Astronomical Society. It was entitled ‘Mary Somerville, the great Woman Astronomer and Mathematician’, and when published in the Society’s Transactions, formed part of that genre of literature in which a person of a younger generation seeks inspiration and direction from the achievements of an illustrious forbear.

Early Life, Career and Friends: The Social World of Georgian Science

Mary Somerville had many blessings. In addition to her obvious intellectual gifts, she had 92 years of active life, an elegance of form which she retained into old age, and a beauty of disposition and a sympathy that gave her the gift of friendship. She was also practical and tough-minded, with no time for woolliness or pretence: a hard-headed individual in a romantic age.