A system of natural philosophy, designed for the use of schools and academies (1845)
Moffat, J[ohn] M. [from old catalog] · Philadelphia, E. C. Biddle · leaf 412
not converge to a focus, so as to form adistinct image on the retina, unless they are relatively at a con-siderable distance from the eye. Hence it happens, as may beoften observed, that aged persons when they attempt to read orexamine a minute object, without spectacles, are usually obligedto hold… … 238. Let C D be supposed to represent a section of the crystal-line lens, and A B a similar section of a spectacle lens, then theobject O, at about six inches from the eye, will form a perfectimage on the retina, at R; but if the latter lens be removed, theobject at the same distance will become…
Physics
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