Mot Dollond uppträdde nämligen helt oväntat, då han sökte patent på sin uppfinning, Chester More Hall med uppgift, att han långt förut konstruerat akromatiska linser, ehuru han ej benämt dem så. Rörande denna sak finnes en not i Philosophical Magazine 1798, vol. II, p. 177,[1] vilken här meddelas:
The inventor was Chester More Hall, Esq. of More Hall, in Essex, who about 1729 as appeard by his papers considering the different humours of the eye, imagined they were placed so as to correct the different refrangibility of light. He then conceived, that if he could find substances having such properties as he supposed these humours might possess, he should be enabled to construct an object glass that would show objects colourless. After many experiments, he had the good fortune to find these properties in two different sorts of glass; and by forming lenses made with such glass, and making them disperse the rays of light in contrary directions, he succeeded. About 1733 he completed several achromatic objectglasses (though he did not give them that name) which bore an aparture of 2½ inches, though the focal lenghth did not exceed 20 inches; one of which is now in the possession of the Rev. Mr. Smith of Charlotte-street, Rethbone Place. This glass has been examined by several gentlemen of eminence and scientific abilities, and found to possess the properties of the present achromatic glasses.
Mr. Hall used to employ working opticians to grind his lenses; at the same time he furnished them with the radii of surfaces, not only to correct the different refrangibility of the rays, but also the aberration arising from the spherical figure of lenses. Old Mr. Bass, who at that time lived in Bridewell Precinct, was one of these working opticians, from whom Mr. Halls invention seems to have been obtained.
- ↑ Observations on Platina and its utility in the arts etc. by Alexis Rochon. (Översatt ur Journal de Physique 1798, vilken journal ej varit mig tillgänglig).
