Oxford: Sheldonian Theatre, 1695.
First edition of this rare work, famous today for its suggestion that an achromatic compound lens might be formed by combining simples lenses of different media. The use of ‘achromatic doublets’ was a crucial step in the further development of telescopes and microscopes.
From Marischal College, Aberdeen, David Gregory (1659-1708) entered Edinburgh University, graduating M.A. on 28 November 1683. A month prior to his graduation he was elected to the Chair of Mathematics, at one time occupied by his uncle, the great mathematician James Gregory, whose Optica promota (1663) had described a reflecting telescope which used parabolic mirrors. As a professor, David Gregory was the first to lecture publicly on the Newtonian philosophy. His lecture notes show that they covered a broad range of subjects including geodesy, optics, dynamics, and various branches of mathematics. Increasingly under attack by his fellow professors at Edinburgh for his radical political views, in 1691 he went to London where he was introduced to Newton and recommended to John Flamsteed, the first astronomer royal. In that same year, Edward Barnard retired from the Savilian professorship of Astronomy at Oxford; backed by Newton’s recommendation of him as ‘very well skilled in Analysis & Geometry both new & old ... understands Astronomy very well ... & is respected the greatest Mathematician in Scotland’, and with Flamsteed’s support, Gregory was elected to the chair in face of strong opposition from Edmond Halley.
As Gregory tells us in the preface, the present work is the printed version of lectures delivered at Edinburgh in 1684, adapted to the teaching of Oxford undergraduates. The passage in which Gregory uses the analogy with the human eye to suggest the construction of an achromatic lens occurs on p. 98: in English translation, ‘Perhaps it would be of service to make the object lens of a different medium, as we see done in the fabric of the eye; where the crystalline humour (whose power of refracting the rays of light differs very little from that of glass) is by Nature, who never does anything in vain, joined with the aqueous and vitreous humours (not differing from water as to their power of refraction), in order that the image may be painted as distinct as possible on the bottom of the eye.’ Whiteside (DSB) suggests that Gregory may have had this insight from Newton.
The work was reprinted at Edinburgh in 1713. An English translation followed two years later with notes by William Browne on refracting telescopes and microscopes; this was republished in 1735 by Desaguliers with an added appendix on the history of the reflecting telescope.
In addition to the present work, Gregory published in 1684 at Edinburgh his Exercitatio geometrica de dimensione figurarum in which, with the assistance of his uncle’s work, he extended the method of quadratures by infinite series; and in 1702 Astronomiae physicae & geometricae elementa, the first textbook of astronomy based on Newtonian gravitational principles.
ESTC R16816; DSB V: 520-1; Honeyman 1550; Poggendorff I, 948; Vagnetti CB1.
8vo (177 x 110 mm), pp. [iv], 99, , with engraved vignette of Sheldonian Theatre on title and numerous woodcut diagrams in text. Contemporary calf, hinges cracked but ties still strong, some chipping to capitals but a nice and unsophisticated copy.