The processes launched at the start of Roman rule continued to support the development of cities and their elites. The 150 years from Hadrian to Diocletian saw enough violence to do severe damage to some of those cities, particularly Alexandria, and occasional revolts disturbed the peace, including one in the Delta at the time of the great plague (smallpox) under Antoninus Pius, which led to the depopulation of many villages. A loss of workers to the plague may have intensified the concentration of landholding in the hands of the wealthy, who could invest in both machinery and capital-intensive crops such as wine. This period also saw the decline of the temples and the beginning of Christianity as a visible (and occasionally persecuted) movement, with the emergence of bishops of Alexandria and the countryside. The Egyptian language acquired a new means of expression in the Coptic alphabet, largely derived from Greek.