But there was a rock on which the luckless adventurer was doomed to split. Humbler patrons than he had found might for a long while have been satisfied with the scanty portion of gold contained in the bottom of a crucible; but the desires of his powerful friends were of a more greedy and impatient kind, not to be fed with distant hopes, but demanding large and immediate fruition. Richelieu loudly called upon the alchemist to operate on an extensive scale; and he proved that it was necessary to do so, by requiring that Dubois should furnish weekly a sum which should not be less than six hundred thousand livres, about 25,000_l._ The startled Dubois requested time to make the requisite preparations, and time was granted. In truth, as the powder of projection was believed to be procurable only by a protracted and laborious process, it was impossible not to admit his claim for delay. The marvel is, that he did not avail himself of the respite, to get beyond the reach of danger. When the day arrived which he had named, he was of course compelled to own that he was not yet prepared. Suspicion being excited, he was imprisoned at Vincennes, whence he was transferred to the Bastile. Offended pride and vanity and disappointed cupidity are often cruel passions. To punish Dubois for his sins against them, the cardinal appointed a commission to try him; but being averse from coming forward in the character of a dupe, he ordered him to be arraigned on a charge of dealing in magic. As the wretched man obstinately persisted in denying his guilt, he was put to the torture. To gain a brief reprieve from his sufferings, he offered to realise the golden dreams which he had excited. Faith was not quite extinct in his patrons, and he was allowed to make another experiment. It is needless to say that he failed. Being thus driven from his last hold, he avowed his imposture, was sentenced to death, and terminated his existence on the scaffold, on the 23d of June 1637.