Honestly it likely won't matter. As long as the element has power running through it it will light up. Try it on a bench vise. You can switch them around touching the white wire to the side and black to the bottom and it will light up without any noticeable difference. But if I remember correctly the bottom should be hot, ie black.
All that said I agree with everyone else, go buy a socket. Open elec. connections are a bad idea.
Edit:
Here's a diagram:
8- Neg.
11- Pos.
But like I said in a basic incandescent bulb it doesn't matter which way the power flows within the bulb itself. As long as 110 goes through that element (#3) it will light.