sentences:  It was achieved by civic effort; the "Central-Dombauverein", founded in 1842, raised two-thirds of the enormous costs, while the Prussian state supplied the remaining third.The state saw this as a way to improve its relations with the large number of Catholic subjects it had gained in 1815, but especially after 1871, it was regarded as a project to symbolize German nationhood.Work resumed in 1842 to the original design of the surviving medieval plans and drawings, but utilizing more modern construction techniques, including iron roof girders.