Awl --
Guess what.... of course it didn't lite up! Seems like the sodium bulbs were mixed in with the metal halide bulbs, in the hardware store, and I was just looking for "70W".
The Q is: Did it harm the ballast? The bulb was in there for a few minutes, while I mucked around (25 feet up in a tree), tryna figger stuff out, before I noticed the "MH" designation on the bulb... A short length of the glass stem glowed very slightly.
So, I disconnected the fixture (70 W) from power altogether, until I can (hopefully) exchange the bulb. I doubt the bulb was harmed. Man, these things aren't cheap.... almost $22 for the metal halide bulb.
These bulbs are really inneresting in design. Not sure what does what, but the insides are neat. I assume most of these bulbs are similar to regular ole fluorescents in principle, where the atom at hand needs to be vaporized, then ionized (ignited), then kept in a steady state current.