What is this box hanging from my car?

[princess]

Image: http://forums.redflagdeals.com/membe...ture1429-a.jpg 2001 Chev Cavalier Z24, located near the back end and approx. in the middleNot sure what this is, but I had driven for a little while with it dragging underneath my car.Talked to my mechanic over the phone, he didn't give me a straight answer but thought it might have something to do with my emissions and said I might be able to disconnect it completely - temporarilyI can't get to my mechanic for another 2 days, and need to get to a few places.. so just looking for some more straight up help on what this thing is, can hopefully what I can do with it until I can get my car into the shop