‘A Less Agreeable Matter’: The Disagreeable Case of Newton and Achromatic Refraction

Abstract

There is no evidence to suggest that even as late as January 1672, when Newton was elected a Fellow of the Royal Society, anyone (except those unknown few who had in the previous years attended his Lucasian lectures at Cambridge) had any inkling of his new theory of colours. His name exploded on the scientific scene as the inventor and constructor of a new kind of telescope—what later became known as the reflector (which was somewhat misleading compared with its name during the seventeenth century: the catadioptrical telescope). Had the erudition of the London virtuosi been a little broader, they would have known that in fact he was not the inventor of the telescope, even though the precise form he gave it was his. Not only was the idea a hundred years old, during which period it was repeatedly suggested by various writers, but also Newton himself took the idea straight from the most recent of these suggestions, namely that included in James Gregory's Optica promota of 1663. The situation becomes even more ironic when we realize that the new instrument was admired for wrong reasons and on merits that were far from Newton's intentions. Nevertheless, admired it was, and there was a good reason for this: Newton's instrument was in fact the first reflector actually to be constructed and, moreover, for a few weeks (before its mirror became tarnished) it performed quite well. Several astonomers became interested because of the high magnifying power relative to its dimensions (about 7 inches long, with a magnification of 38).