The Wigan pit brow girls in the Victorian society wore trousers for their dangerous work in the coal mines. They wore skirts over their trousers and rolled them up to their waist to keep them out of the way.
Those young women worked often in mines where metal ores (copper or tin) were extracted, while their fathers, brothers or husbands were down below.
The tasks included often crushing large pieces of stones to expose more ore.
They are heroic because they were not forced to work so hard, but did so by choice to better themselves and help their families.
The constrictions of the Victorian life were almost like those of its chief social and physical prosthesis -> the corset.