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.
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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.
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.
Regarding various types of glass for lenses. Will make two of JH's reading glasses if he will send details.
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 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.