Answer:
As I went over London Bridge I met my sister Jenny; I broke her neck and drank her blood and left her standing empty.
Lovely and round, I shine with pale light, Grown in the darkness, a ladyβs delight.
I run up and down the stairs without moving
If you break me, I'll not stop working. If you can touch me, my work is done. What am I?
Break me and I am better, immediately set and harder to be broken again. What am I?
Almost everyone needs it, asks for it, gives it. But almost nobody takes it.