“Look,” said he to the procureur, whose heart beat so loudly that it might almost be heard, “here is in this cup some syrup of violets, and this decanter contains the remainder of the lemonade of which M. Noirtier and Barrois partook. If the lemonade be pure and inoffensive, the syrup will retain its color; if, on the contrary, the lemonade be drugged with poison, the syrup will become green. Look closely!”

The doctor then slowly poured some drops of the lemonade from the decanter into the cup, and in an instant a light cloudy sediment began to form at the bottom of the cup; this sediment first took a blue shade, then from the color of sapphire it passed to that of opal, and from opal to emerald. Arrived at this last hue, it changed no more. The result of the experiment left no doubt whatever on the mind.

“The unfortunate Barrois has been poisoned,” said d’Avrigny, “and I will maintain this assertion before God and man.”