From this page http://freepages.genealogy.rootsweb.ancestry.com/~todmordenandwalsden/derdalemill.htm#anchor1
On July 18, 1879, a terrible accident occurred. The flywheel from a weaving shed engine exploded into pieces, killing a woman named Sarah Pilling and injuring two others, Mary Escritt and Mary Mills.
There was extensive damage to the property. An Inquest jury later returned a verdict of accidental death on Sarah Pilling.
Derdale Mill was situated next to the Key Sike Lane bridge opposite Sandholme Mill.