Dolland, although in 1753 he strongly supported Newton’s error in a Royal Society paper against Euler’s belief in achromatism, shifted his view a couple of years later and after a considerable period of skilful and well ordered experimenting published his discovery of achromatism early in 1758, for which a patent was granted him April 19, while in the same year the Royal Society honored him with the Copley medal. From that time until his death, late in 1761, he and his son Peter Dolland (1730-1820) were actively producing achromatic glasses. The Dollands were admirable craftsmen and their early product was probably considerably better than were Hall’s objectives but they felt the lack of suitable flint and soon after John Dolland’s death, about 1765, the son sought relief in the triple objective of which an early example is shown in Fig. 18, and which, with some modifications, was his standard form for many years. [Illustration: FIG. 18.—Peter Dolland’s Triple Objective.] Other opticians began to make achromatics, and, Peter Dolland having threatened action for infringement, a petition was brought by 35 opticians of London in 1764 for the annulment of John Dolland’s patent, alleging that he was not the original inventor but had knowledge of Chester Moor Hall’s prior work. In the list was George Bast, who in fact did make Hall’s objectives twenty five years before Dolland, and also one Robert Rew of Coldbath Fields, who claimed in 1755 to have informed Dolland of the construction of Hall’s objective. This was just the time when Dolland came to the right about face on achromatism, and it may well be that from Rew or elsewhere he may have learned that a duplex achromatic lens had really been produced. But his Royal Society paper shows that his result came from honest investigations, and at worst he is in about the position of Galileo a century and a half before. The petition apparently brought no action, perhaps because Peter Dolland next year sued Champneys, one of the signers, and obtained judgment. It was in this case that the judge (Lord Camden) delivered the oft quoted dictum: “It was not the person who locked up his invention in his scrutoire that ought to profit by a patent for such invention, but he who brought it forth for the benefit of the public.[7]” [7] Commonly, but it appears erroneously, ascribed to Lord Mansfield. This was sound equity enough, assuming the facts to be as stated, but while Hall did not publish the invention admittedly made by him, it had certainly become known to many. Chester Moor Hall was a substantial and respected lawyer, a bencher of the Inner Temple, and one is inclined to think that his alleged concealment was purely constructive, in his failing to contest Dolland’s claim.