 In 1747 the Colleges of St Leonard's and St Salvator's were combined into the United College, with the University now led by two principals.The modern office of Principal dates from 1858, with the passage of the University (Scotland) Act 1858.From 1858 until 1889 the senior of the two Principals (of the United College or St Mary's) undertook the responsibilities of Principal of the University, when in 1889 the Principal of the United College was made Principal of the University.