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<p>Book digitized by Google from the library of the New York Public Library and uploaded to the Internet Archive by user tpb.
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<br>Subjects: rays; pencil; image; angle; lens; focus; incident; focal; refraction; ray; focal length; magnifying power; parallel rays; principal focus; conjugate foci; principal focal; emergent rays; second surface; focal lengths; refracted rays</div>
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Richard Potter</div>
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