Sorrenson – Perfect Mechanics

Sorrenson, Richard, Perfect Mechanics. Instrument Makers at the Royal Society of London in the Eighteenth Century, Boston: Docent Press, 2013, ix+240 pp. Amazon link.

Perfect Mechanics looks at the connections, and tensions, between the Eighteenth-Century mathematical instrument makers and the Royal Society. In this highly-readable and well-researched adaptation of a Princeton Ph.D., Sorrenson blends together over-arching themes with detailed case studies.

If the Royal Society was an elite club for philosophical gentlemen, what were mere artisans doing there? Sorrenson shows that both halves of this thesis are flawed. Although a Royal Society, and chartered by Charles II, the Society was largely neglected by indifferent sovereigns. While an interest in the workings of the society and sufficiently high rank was a guarantee of membership, the remainder of the fellows formed a more diverse group than might be imagined. While social status was an advantage, membership could be achieved through diligent study, patient observation, and significant contribution to the body of knowledge, regardless of class. While the Society depended for its continued existence on a group of (largely) landed gentry who paid their dues and took their copies of the Society’s journal of record, the Philosophical Transactions, but played little active part in the working of the organization, the active Fellows spanned a range of social class.

The Society’s mission was exploration of the modern experimental and natural philosophies, but in outlook they were more Baconian than Newtonian. Observation and experimentation were prized above abstract theorizing. “To the eighteenth-century Fellows of the Royal Society, the ideal scientific life was exemplified by those members who made careful observations of natural or artificial phenomena, gave them a mechanical explanation or demonstration where possible, avoided grand theory, and above all produced reliable and accurate facts” (35). Newton cast a long shadow. Sorrenson notes that pure mathematics makes up some 2% of all papers published in the Philosophical Transactions.

Behind the search for reliable and accurate facts lay the instruments, and the instrument makers. The eighteenth century saw the introduction of a host of observation instruments, and the refinement of others, from telescopes and microscopes, to vacuum pumps, barometers, hydrometers and clocks. Observations with these instruments greatly augmented natural human senses and as the facts became more accurate and precise, they uncovered new, unexpected phenomena. The gentlemen philosophers needed close interaction with the artisans, and here we come to the second part of Sorrenson’s analysis. While instrument makers for the regular trade could be seen just as craftsmen, working with their hands for commercial gain, those at the cutting edge of instrument design needed both a practical ability and theoretical background. A few instrument makers at the top of their profession made their own discoveries, published in the Philosophical Transactions, were awarded the Copley Medal, the Society’s highest honor, and were welcomed as Fellows. Sorrenson presents three case studies, for the early part of the century, the middle and the latter decades.

First is George Graham (1673—1751). Praised for the great mural quadrant he designed and made for Edmond Halley for the Greenwich Observatory, an instrument of unsurpassed accuracy, Graham regularly published his own astronomical observations in the Philosophical Transactions, and the great accuracy of his instruments allowed the discovery of the new phenomenon of the aberration of starlight, a discovery in which he himself played a significant part.

Graham also discovered the diurnal variation in the Earth’s magnetic field by the expedient of making a superbly accurate compass and taking careful measurements several times a day for two solid years. An exemplar of the governing philosophy of science. Graham had trained as a clockmaker under Thomas Tompion. The rate of a pendulum clock depends on the length of the pendulum, and this varies with temperature as the length of the pendulum increases in warmer weather and decreases in colder weather. Therefore a clock will not beat steady time over the year. Graham devised a way of attaching a mercury column to the pendulum to exactly counter this effect, and this is the instrument displayed behind him in the portrait above (from an engraving by J. Faber after Thomas Hudson).

Sorrenson’s second case is the Dollond family, especially John Dollond (1706—1761). The Dollonds were opticians, and, along with spectacles, the main optical instrument of the mid-eighteenth century was the telescope. Telescopes are either reflecting (using mirrors) or refracting (using lenses). When light passes through a lens, the material bends, or refracts, the light. However, the amount the light is bent depends on the wavelength, with the blue and red bending through different angles. This is the phenomenon that allows a prism to split up white light. However, in a telescope, it means that white starlight gets smeared with colored fringes, a problem known as chromatic aberration that limits the accuracy of observations. John Dollond found a way two put two lenses of different types of glass together (crown and flint) to cancel out the effect. Not only did this immediately make refractive telescopes better (and sweep the market), but Isaac Newton had investigated the issue and stated flatly that it could not be solved. Dollond had bested Newton.

The third case is Jesse Ramsden (1735—1800), who married John Dollond’s daughter, Sarah. At the height of his career, Ramsden made the best instruments available. Orders poured in from observatories and kings across Europe. His extreme accuracy was matched only by his extreme dilatoriness. If you wanted a Ramsden instrument, you had to wait. He made enormous vertical circles, one seen in the background, used by astronomers to create improved star catalogs, and he designed and built the enormous theodolite used for the first Ordnance Survey of England. Ramsden’s other claim to fame, also shown in his portrait, is the dividing engine. This apparatus allowed and journeyman or apprentice, to divide a surveying instrument with the accuracy previously only available to the most skilled craftsmen. With this, he could produce cheaper and better sextants and other instruments for the insatiable navigational market, but the price for the profession was a loss of status. From experts mixing theoretical philosophy with practical mechanics, they became machine-tool users. The delicate social balance between gentlemen and instrument makers was being lost.

Sorrenson’s argument for how the instrument makers achieved social status, and how they lost it, is carefully made. The book contains a wealth of detail (and characters) not touched on here, all told with an ease that litle academic scholarship attains. Perfect Mechanics is an important account of a crucial period of development in British science and industry showing how philosophy, economics, social manners and technology blended together.


One thought on “Sorrenson – Perfect Mechanics

  1. Pingback: No Mathematics! | Kirby and his world

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