III. Six Books on Light and Shade: 197.

197.

A luminous body which is long and narrow in shape gives more confused outlines to the derived shadow than a spherical light, and this contradicts the proposition next following: A shadow will have its outlines more clearly defined in proportion as it is nearer to the primary shadow or, I should say, the body casting the shadow; 96 the cause of this is the elongated form of the luminous body a c, &c 97 .