black and red lines

Ingredients

black ink, red ink

Preparation Steps

Original Recipe Text

The drawing procedure begins by sketching the circle and the burning-cone (p. 165). From the midpoint 'l' of the eye, an axis 'la' is drawn (p. 165). The diagram uses color to facilitate understanding: lines originating from the right side of the observer's eye are drawn in black, while those from the left are drawn in red (p. 165). These color-coded lines allow for the tracking of rays undergoing single or double refraction and reflection (p. 165-167).

Evidence

"By means of the adjacent figure (with black and red lines in the manuscript) Kamāladdħn describes the procedure"

Remarks

Kamāl al-Dħn al-Fārisħ (d. 1318) utilized a distinct color-coding system in his diagrams for 'Tanqħሐ al-Manāሙir' to illustrate optical phenomena. The text notes that right-side rays (lb, lg, ld, le) are deflected toward specific chords and drawn in black, while left-side rays (lj, lk, lm, ln) are deflected toward others and drawn in red (p. 165). This differentiates rays reflected and refracted once from those reflected twice (p. 165). The figures were notably added to overcome the absence of such diagrams in earlier manuscripts of Ibn al-Haytham's work (p. 164, 170).