like Schmallenberg with its concentration on , saw new industrial developments. The expansion of also slowed. As the nineteenth century progressed, the coal mining industry in the Ruhr grew ever stronger. In the 1850s, Hermannshütte, Rothe Erde, , , and in Hattingen were established. As a result, some of the pre-industrial areas in Westphalia became marginal and were only able to succeed by concentrating on particular products (e.g. lead production in ). Even more new pit mines and mining companies were established in the Ruhr region in the following years, such as the . Moreover, older factories grew into massive enterprises with several thousand employees. By the middle of the nineteenth century at the latest, the Westphalian portion of the Ruhr was clearly the economic centre of the province. Population growth and social change The developing industry initially pulled numerous jobseekers mostly from the agriculturally and economically stagnant parts of the province. From around the 1870s, the supply of workers within Westphalia was exhausted and companies increasingly drew workers in from the eastern provinces of Prussia and beyond. The large number of Polish-speaking workers established their own societies, labour unions and pastoral care organisations, which operated in their own language. A particular population profile developed in the mining districts, which differed from the rest of Westphalia in some respects, such as dialect (Ruhrdeutsch). In 1871, the province of Westphalia had 1.78 million inhabitants, around 14% more than in 1858. By 1882, the population had grown more than 20% and the growth from then to 1895 was similarly high. In the ten years between 1895 and 1905, the population grew by more than 30%, surpassing 3.6 million. The highest growth took place in Arnsberg district, the centre of Westphalian industry. Between 1818 and 1905, the population of Münster and Minden districts grew by slightly more than 100%, but that of Arnsberg grew by over 400%. In all the industrialised areas of Westphalia, but especially in the Ruhr, the social consequences of industrialisation were substantial. In these areas, the working class became the largest social group by some margin. Immigration meant that the population growth over time was erratic. The supply of housing was insufficient and, in the Ruhr, lodgers and (people who rented a room for only a couple of hours a day) were common. Corporations sought to plug this gap to some extent with company housing or workers' settlements. The