Journal - Franklin Institute of the State of Pennsylvania (1826)
Franklin Institute, Philadelphia, Franklin Institute (Philadelphia, Pa.) · [Philadelphia : Franklin Institute] · leaf 486
es of the centre appear straight; the othersappear curved. When the upper is in the reverse position to the lowerone, they appear pincushion shaped. When distortion of the negativelens is reversed, the lines appear as the curved sides of a barrel.The cause of distortion is somewhat difficult to… … Fig. 30
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