Informs JH that he is taking over the optical workshop of his late father-in-law, Andrew Ross.
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Informs JH that he is taking over the optical workshop of his late father-in-law, Andrew Ross.
Answers JH's inquiry concerning JD's telescope manufacturing process.
Thanks for his note on the performance of the telescope. Gives suggested reasons for faults. Sends a print of a photograph of a map recently taken by one of his achromatic lenses.
Outlining phenomena in the refraction of light. Has been experimenting with wide angle lenses for cameras and gives some of their defects. Would like JH's opinion on how to get rid of the 'secondary focus.'
Has not had time until now to carry out experiments on 'the central spot' as seen in photographs as related in JH's last letter. His recent trials with various lenses have verified JH's theories.
Regarding various types of glass for lenses. Will make two of JH's reading glasses if he will send details.
Thanks for letter and details of his paper in the R.S.P.T. Wishes there was an index of authors and subjects for students. Theories regarding the action of light on glass. Has interested Messrs. Chance in his theories. Gives reasons why he wants a reading glass of 3 1/2 inches.
Has made a trial of JH's lens but it was too large to be satisfactory. Regarding the 'graphoscope,' a new toy. Has been concerned with the manufacture of an improved form of opera glass. Present forms have many imperfections. Gives details of his own theories and sends one for JH's notice.
Thanks for his letter. Is glad the binoculars give a satisfactory performance, but regrets the width between the tubes does not suit JH's eyes. Will alter this and send a new pair later.
Provides a physical explanation for a white patch in the center of JD's photograph.
Is he acquainted with his ordinary reading glass? Gives details. Always carries a small one around with him for reading small print; thinks there would be a good market for them.
Outlining suitability of various types of glass for optical work. Gives details of theories of his reading lenses and calls attention to one of his own papers in the R.S.P.T. for 1821.
Thanks and a detailed description of the functioning of a pair of binoculars sent by JD to JH.