what everyone else said!
or as i see it, neutral and ground are probably tied together in your service panel.. so you have a ground on your one circuit, the neutral ties it in again, THEN you want to tie that ground to another circuit's ground/neutral for redundancy? do you have a big squirrel problem in your walls and need so much duplication?
good luck and don't do it, you'd be killing unnecessary copper trees....
or as i see it, neutral and ground are probably tied together in your service panel.. so you have a ground on your one circuit, the neutral ties it in again, THEN you want to tie that ground to another circuit's ground/neutral for redundancy? do you have a big squirrel problem in your walls and need so much duplication?