beyond its apex this gives rise to a second pyramid; this is what is spoken of at the beginning of No. 166.]
167.
The cast shadow will be longest when the light is lowest.
The cast shadow will be shortest when the light is highest.
168.
Both the primary and derived shadow will be larger when caused by the light of a candle than by diffused light. The difference between the larger and smaller shadows will be in inverse proportion to the larger and smaller lights causing them.
[Footnote: In the diagrams A stands for celo (sky), B for cadela (candle).]
169.
ALL BODIES, IN PROPORTION AS THEY ARE NEARER TO, OR FARTHER FROM THE SOURCE OF LIGHT, WILL PRODUCE LONGER OR SHORTER DERIVED SHADOWS.
Among bodies of equal size, that one which is illuminated by the largest light will have the shortest shadow. Experiment confirms this proposition. Thus the body m n is surrounded by a larger amount of light than the body *p