VI. These were only vague promises which the Ministry never intended to fulfil. The Cardinal had made no secret[361] of his desire to gain the Duke of Weymar by giving him his niece in marriage: the Prince's refusal and his desire to keep Brisac had so much offended his Eminence, that he even told Erlac that the Duke hearkened to bad counsels, and that his behaviour to France was not such as gratitude and civility required. The malevolence of the French Minister[362] chagrined the Duke so much that he fell ill: it was only a slight indisposition, but, however, he did not long survive it[363]: a violent fever seized him at Neubourg, which on the fourth day cut off a Prince, whom Grotius calls the honour and last resource of Germany[364]: the tenth of July, 1639, was the last of this illustrious personage. It was at that time very doubtful[365] whether he died of the plague, which prevailed in those parts, or of poison. Grotius tells us[366], that the Duke himself thought they had shortened his days: he even cites on this subject the Prince's funeral oration delivered at Brisac, wherein the author was not afraid of advancing this anecdote. Grotius was also persuaded[367] that the Prince died by poison: he mentions it in a letter to the High Chancellor of the 10th of October, 1639. "The more I reflect on the Duke of Weymar's death, the more I am persuaded that he had on his body no marks of the plague, and that it was not in his house: accordingly the reports of his being poisoned again prevail, and the suspicion falls upon the Geneva physician, who was brought to remove his cholic."