similar to those of the real rainbow. They may also be seen when oil has been placed on the top of water and in the solar rays reflected from the surface of a diamond or beryl; again, through the angular facet of a beryl every dark object against a background of the atmosphere or any thing else equally pale-coloured is surrounded by these rainbow colours between the atmosphere and the dark body; and in many other circumstances which I will not mention, as these suffice for my purpose.
VI.
'Prospettiva de' colri' (Perspective of Colour)
and
'Prospettiva aerea' (Aerial Perspective).
Leonardo distinctly separates these branches of his subject, as may be seen in the beginning of No. 295. *Attempts have been made to cast doubts on the results which Leonardo arrived at by experiment on the perspective of colour, but not with justice, as