In one of the letters of this celebrated philosopher, he says, that he was consulted by his friend and patron the Count d'Alais, governor of Provence, on a phenomenon that haunted his bed-chamber while he was at Marseilles on some business relative to his office. The Count tells Gassendi, that, for several successive nights, as soon as the candle was taken away, he and his Countess saw a luminous spectre, sometimes of an oval, and sometimes of a triangular form; that it always disappeared when light came into the room; that he had often struck at it, but could discover nothing solid. Gassendi, as a natural philosopher, endeavoured to account for it; sometimes attributing it to some defect of vision, or to some dampness of the room, insinuating that perhaps it might be sent from Heaven to him, to give him a warning in due time of something that should happen. The spectre still continued its visits all the time that he staid at Marseilles; and some years afterwards, on their return to Aix, the Countess d'Alais confessed to her husband, that she played him this trick, by means of one of her women placed under the bed with a phial of phosphorus, with an intention to frighten him away from Marseilles, a place in which she very much disliked to live.