Why would so many women miners prefer to work in the mines without clothing? Why did the women need the heavy belts around their waists and chains between their legs?

Answer 1

Read these very descriptive sites.

http://www.womeninworldhistory.com/coalMine.html

http://www.historylearningsite.co.uk/coal_mines_industrial_revolution.htm

Answer 2

They would need to work in the mines without clothing because the conditions were poor and time was being wasted a lot for them "dressing up". They needed heavy belts around their waists and chains between their legs so they could take the corves (wagons) out of the mines.