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specified by you - viz to produce an image 22^c at a distance of 50^c

The colored fringes mentioned by you are simply due to aberration from diffraction, an account of the aperture of diaphragm not being sufficiently large, and this I think will vanish when you have removed the circular ring containing the cross wire

Awaiting the favor of your reply

I am, Rev^d Sir,
Yours most Obediently
J.H. Dallmeyer

The Rev^d P.A. Secchi

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