sentences:  The Prussian and then German period lasted for about 180 years and overlapped with the time of rapid industrialization.With the discovery of bituminous coal deposits at the end of the 18th century by the Polish local priest Ludwik Bojarski, new industrial sectors developed in the Chorzów area.In the years 1791–1797 the Prussian state-owned Royal Coal Mine was constructed ("Kopalnia Król", "Königsgrube", later renamed several times with the changing political winds).