MYDORGE, Claude.

Parisiis: Ex typographia I. Dedin… 1631

Small folio, 6 leaves (including the initial blank), 134 pages, 2 leaves (errata). Woodcut device on title, woodcut head- and tailpieces and initials, diagrams in the text. Comtemporary vellum. This copy has been water-damaged at an early stage; the front endpapers and the initial blank are ragged, and the fore-edge and lower margins of the title-page are partly missing, the vellum is a bit stained and the paper is wrinkled but otherwise in good condition and only very lightly discoloured or stained. Presentation copy, inscribed by the author in the lower margin of the title-page to Christian S. Zeuggman, and signed by Mydorge with his full name rather than usual sign “D.A.L.G.”

FIRST EDITION of Mydorge’s important and original work on conic sections, presented as a geometric basis of reflective and refractive optics. “In his study of conic sections Mydorge continued the work of Apollonius, whose methods of proof he refined and simplified… Mydorge asserts that if from a given point in the plane of a conic section radii to the points of a curve are drawn and extended in a given relationship, then their extremities will be on a new conic section similar to the first. This statement constitutes the beginning of an extremely fruitful method of deforming figures; it was successfully used by La Hire and Newton, and later by Poncelet and, especially, by Chasles, who named it déformation homographique… Mydorge’s works on conic sections contain hundreds of problems published for the first time, as well as a multitude of ingenious and original methods that later geometers frequently used, usually without citing their source.… Finally it should be noted that the term ‘parameter’ of a conic section was introduced by Mydroge” (DSB). “By the time of the Prodromi, Mydorge had intimate knowledge of the optical properties of curves and surfaces and had developed descriptions based not on their figures as produced by sectioning a cone, but rather on their focal properties. He was equally interested in, and inventive of, ways in which to actually produce these curves. Both aspects would define the Prodromi” (DiLaura). This first edition contains the first two Books, and is much rarer than the second edition of 1639 which contained all four Books. As in the Columbia, BNF and Horblit (now at Zürich) copies (and possibly in the only other copy recorded by OCLC, at NYPL), this copy has a manuscript correction relating to page 36 signed “D.A.L.G.” and a small stamp with the author’s arms in the lower margin of the first page of errata. DiLaura, Bibliotheca Opticoria, 71.

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