In 1785 he was invited to University of Padua, but to retain his services his sovereign doubled his salary and allowed him leave of absence for a visit to Turkey where he remained nearly a year and made many observations, among which may be noted those of a copper mine in Chalki and of an iron mine at Principi. His return home was almost a triumphal progress: at Vienna he was cordially received by Joseph II and on reaching Pavia he was met with acclamations outside the city gates by the students of the university. During the following year his students exceeded five hundred. While he was travelling in the Balkans and to Constantinople, his integrity in the management of the museum was called in question (he was accused of the theft of specimens from the University's collection to add to his own cabinet of curiosities), with letters written across Europe to damage Spallanzani's reputation. A judicial investigation speedily cleared his honour to the satisfaction of some of his accusers. But Spallanzani got his revenge on his principal accuser, a jealous colleague, by planting a fake specimen of a composite "species". When his colleague published the remarkable specimen Spallanzani revealed the joke, resulting in wide ridicule and humiliation.