Warren, Samuel Edward, 1831-1909. [from old catalog] · New York, J. Wiley & sons · leaf 110
the horizontalprojection of a ray through the intersection of these shadows,gives/ which, projected in CM, at/7, gives fif as the point ofshadow required. Second Method.—This is a special method which may be calledthe method by helical translation of a plane of rays containing anassumed element.… … VI. vin
Shades and shadows
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