Complex sentence: On the death of Archbishop Laurence of Cashel in 1838, the Province of Cashel was united to the Province of Dublin and the see ceased to be an archbishopric; becoming the bishopric of Cashel and Waterford.
Split into simpler sentences: On the death of Archbishop Laurence of Cashel in 1838, the Province of Cashel was united to the Province of Dublin. The see ceased to be an archbishopric ecoming instead the bishopric of Cashel and Waterford.