The children of the poor were expected to help towards the family budget, often working long hours in dangerous jobs for low wages. Agile boys were employed by the chimney sweeps; small children were employed to scramble under machinery to retrieve cotton bobbins; and children were also employed to work in coal mines, crawling through tunnels too narrow and low for adults. Children also worked as errand boys, crossing sweepers, shoe blacks, or sold matches, flowers, and other cheap goods. Some children undertook work as apprentices to respectable trades, such as building, or as domestic servants (there were over 120,000 domestic servants in London in the mid 19th century). Working hours were long: builders might work 64 hours a week in summer and 52 in winter, while domestic servants were theoretically on duty 80-hours a week.