Answers JH's inquiry concerning JD's telescope manufacturing process.
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Answers JH's inquiry concerning JD's telescope manufacturing process.
Informs JH that he is taking over the optical workshop of his late father-in-law, Andrew Ross.
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.