shipyard in Ruhrort for the construction of steamers. 1837 – a shaft of the Kronprinz Mine (on the boundary of present-day Essen and Mülheim) succeeds for the first time in boring through the overlying chalk seam in the Northern coalfield to reach the coal seams below). 1838 – The Gesellschaft der Hardenbergischen Kohlebergwerke is the first joint stock company in the Ruhr. 1839 – According to the Prussian Regulativ über die Beschäftigung jugendlicher Arbeiter in den Fabriken (regulations on the employment of young workers in factories), the minimum age for child workers is nine years old and their working time is restricted to ten hours a day. Children cannot be employed on Sundays and Bank Holidays or during the night. 1839 – In the Gutehoffnung Smeltery, their first steam locomotive is built – called the Ruhr. 1847 – Opening of the Cologne-Minden Railway. It is decisive for the industrial development of the Ruhr and follows the valley of the Emscher, via Duisburg, Oberhausen, Altenessen, Gelsenkirchen, Herne, Castrop und Dortmund, and from there further to Hamm and via Bielefeld to Minden. 1839 – Even while the railway was still being built in the northern part of the Ruhr, the Cologne banking house of Camphausen und Schaafhausen started to interest themselves in the resulting potential for growth in the Emscherland. The Cologne Mining Association was founded as an early Aktiengesellschaft of Ruhr mines (including shaft mines) in Northern Essen, among them the Carl Mine. 1847 – The first steam locomotive to travel along the Ruhr valley, on the Steele-Vohwinkler Railway 1849 – For the first time in the Ruhr, coke was used for steel production – in the Frederick William Smeltery in Mülheim. Second half of the 19th century – industry booms The advances made in the first half of the century were built upon, producing a significant advance in production. In 1850, the district produced 2 million tonnes of coal, by 1913 it produced 114 million tonnes. Likewise, in 1850 it produced 11,500 tonnes of cast iron which rose by 1913 to 8.2 million tonnes. Coal production moved northwards as steam engine technology allowed the exploitation of deep coking coal seams (the earlier mines, generally nearer the River Ruhr, had tended to be drift mines exploiting the anthracite lying nearer the surface). 'Vertical' concerns came into being, with collieries, cokeries and ironworks under common ownership, and it was not uncommon to