On a similar vein (no pun intended!) to the question below, how did they sink coal shafts hundreds of feet in depth vertically years ago? I'm currently reading a book on coal mining in my area and the book seems to evade this issue. I can well understand the use of picks and shovels to dig the horizontal adits but how do you dig a hole to that sort of depth without it collapsing?
Fred Dibnah showed how they did this on one of his TV progs. I think it was the one where he built a miniature coal mine in his back garden! I'm glad I don't live next door to him:-)