MOLYNEUX, William.

Dioptrica nova. A Treatise of Dioptricks, In Two Parts.

Wherein the Various Effects and Appearances of Spherick Glasses, both Convex and Concave, Single and Combined, in Telescopes and Microscopes, Together with Their Usefulness in many Concerns of humane life, are explained.

London: for Benj. Tooke, 1692 Stock Code: 80630

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First edition of the first treatise on the subject to be published in English. Molyneux, who has a claim to be considered the founder of modern science in Ireland, based his book on his discourses to the Dublin Philosophical Society delivered between 1683 and 1686 on the illusion of the different magnitudes of the horizontal and meridional moon, on double vision, and on why four glasses in a telescope show objects erect. The first part presents 59 propositions on geometrical optics, providing a thorough treatment of the nature of sight and the properties of lenses, telescopes, microscopes, and magic lanterns. The second part consists of a series of chapters on topics including refraction and light, glasses for defective eyes, and telescopic instruments. A second edition was published in 1709.

The manuscript was seen through the press by Edmond Halley, who allowed Molyneux to include as an appendix his theorem for finding the focus of a spherical lens. Although Molyneux also acknowledged his obligation to John Flamsteed, who had lent him instruments, and gave the solutions of Flamsteed for certain propositions in addition to his own, the publication led to their falling out, probably because Flamsteed resented that the manuscript was not shown to him before publication but entrusted instead to his rival Halley.

The book brought Molyneux to the attention of Leibniz - whose refutation of Descartes's explanation of refraction and doctrine of final causes were both warmly approved by Molyneux - and Huygens, then the foremost authority on optics. It also led to a key friendship with John Locke, who took Molyneux's criticisms and suggestions into account in the second edition of his Essay on Human Understanding, notably "the so-called Molyneux problem, included as an addition to the chapter on perception. The question posed was whether a blind man who had learned to distinguish by touch between a cube and a sphere would be able, on gaining his sight, to differentiate the objects without touching them. Molyneux thought not and Locke agreed. The problem had profound philosophical implications and became a key topic in British philosophy" (ODNB).

The first edition is notably rare in commerce, having appeared at auction only twice in the past 46 years.

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Quarto (240 x 183 mm). Contemporary blind-panelled calf, sometime rebacked with gilt spine, red morocco label, relined to style. Housed in a brown cloth flat back solander box by the Chelsea Bindery.


Complete with initial imprimatur leaf and final advert leaf. 43 engraved plates (most folded), diagrams, tables in the text.


Short closed tear at foot of imprimatur leaf with old repair, wormhole (mostly single, becoming double) at lower outer corner through to quire O, mostly beyond the text, very occasional minor damping at fore-edge margin, 4 plates to the appendix on browned paper; overall, a very good copy.


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