Directions for using the Achromatic Pocket Perspective Glass or Galilean Telescope with the Stand as represented in the Plate / Directions pour se servir de la Lunette Galiléenne, ou, Perspective Achromatique de Poche avec le Pied comme representé dans la Planche
Autore: DOLLOND & CO.
Tipografo:
Dati tipografici: [London], [ca. 1757]
Large broadsheet (496x367 mm) folded in four, containing in the upper half an illustration (213x288 mm) of Dollond's telescope engraved by Adam Smith and, in the lower part, the explanatory text in English (on the left side) and French (on the right side). The name “Dollond London” is written on the telescope in the engraving. On the verso, which is blank, contemporary manuscripts notes “N-2°-” and “N.° 1.-”. Small tear at the center of the sheet with no loss, some light marginal staining, small loss of paper on left-hand blank margin.
Extremely rare broadsheet advertising the new achromatic telescopes invented in 1757 and patented in 1758 by John Dollond, and produced by his son Peter.
“In the history of patents, the 1763-1766 lawsuit of the English instrument maker Peter Dollond (1731-1821) to implement his exclusive rights to manufacture achromatic telescopes, thanks to the fact that in 1758 his late father John Dollond (1706-1761) had patented the technique, is a well-known case. It is famous, not only because the achromatic telescope disproved Newton's celebrated theorem that the segregation of colours due to refraction cannot be reversed, but also because it is a classic example of a battle over priorities […] In his Opticks of 1706, Isaac Newton had asserted that it was theoretically impossible to correct chromatic aberration using a colour dispersion-free – or so-called ‘achromatic' – telescope. In 1747 the Swiss mathematician Leonard Euler argued that Newton was wrong, since the human eye possessed such a lens. A combination of lenses with differing refractive indices would undoubtedly be able to correct chromatic aberration […] In 1757, Dollond succeeded in manufacturing a telescope that was effectively achromatic, by using a combination of lenses with differing refractive indices, made from flint glass and crown glass. In 1758 Dollond's publication of the results [An Account of some Experiments concerning the Different Refrangibility of Light, in: “Philosophical Transactions”, 1, 1758, pp. 733-743] made a considerable impact on the scientific community […] As John Dollond's son Peter had started an instrument-making business in 1750, in which John as father also participated commercially, Dollond Senior also applied for a patent for his invention. In those days a patent was of importance foremost as a way to improve the marketing of an instrument. After John Dollond's death in November 1761, Peter Dollond decided to use the 1758-patent to enforce a monopoly on the manufacture of the achromatic telescope. In a number of legal procedures he summoned to court a number of London-based instrument makers who, in the intervening years, had successfully manufactured and copied John Dollond's achromatic telescope” (H.J. Zuidervaart, The Evasion of Dollond's Notorious Patent on the Achromatic Telescope by the Move to the Dutch Republic of the Instrument Makers Eastland and Champneys, in: “Bulletin of the Scientific Instrument Society”, 128, 2016, p. 24 ff.).
“John Dollond (1706-61), English optician, the son of a Huguenot refugee; he was born in Spitalfields, London and started work as a silk weaver. In his spare time he studied hard at mathematics, physics, Latin and Greek. In 1752 he gave up his weaving and joined his eldest son, Peter Dollond (1730-1820), who two years previously had set up in business making optical instruments in St Paul's Churchyard. The firm became known as Dollond & Co. His experiments resulted in a number of advances including a means of making achromatic lenses from crown and flint glasses, the production of refraction without colour by the aid of glass and water lenses and later the same result by a combination of different quality glasses […] This ‘achromatic' or ‘free from colour effects' telescope is the type normally used for astronomical or terrestrial observation” (J. F. Mills, Encyclopedia of antique scientific instruments, New York, 1983, pp. 104-105).
Museo Galileo, MED 1816/11.
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