Of course, both these folks are exactly correct...but to explain a bit furthur...

The positive current carrying wire comes from the ignition switch, and that is the one that is in the metal shroud that goes under the dash between the ignition switch and the coil. You don't see this one from under the hood.

The negative wire is the one that goes from the side top of the coil to the points. The points basically (literally actually) turn the coil on and off by completing the ground circuit every time there needs to be a spark. Part of that ground circuit goes through the points spring...hence, if that spring is touching the side of the distributor, the coil will be on all the time, and they don't work that way. For this reason, you would never get any voltage at the wire on the side of the distributor, because it is negative...not positive.

You can check for spark at the points if you like too... take the cap and rotor off, rotate the engine till the points are closed, then manually open them with a plastic knofe or something. If they don't spark when you open and close them, there is something wrong...and its probably the spring and insulators previously mentioned. Also...did you change the condensor? Make sure that's tight and well grounded. I'm sure its not your problem though....

Good luck!
-Matt