I'm trying to wrap my head around how to get this done:

I've got a light fixture in my basement with a pull string. I've got a source line coming in, and three more lines going out of the fixture.
One goes to another light fixture about 6' away. That fixture is controlled by a switch. I'd like to wire the pull string light to the same switch.
Running another line isn't a showstopper, but I've got a vague feeling that I shold probably be able to do this with the wiring I've got. I hooked
another light up to a switch with the source at the light, but the extra fixture in this instance is making my head explode.

Here's a brilliant artistic rendering of the situation, any idea on how to wire that up? Based on the other work I've done here, I believe the wiring
is all 2 wire (black, white, bare copper).

Well, the switch should be between the power source and the load that is to be switched by it, assuming it is a single switch system. Things get more complex when you have a dual switch system, (such as one at two different doors to the same room).

Are you able to physically see (and trace) all that wiring, or are you concluding that wires in the wall are wired that way? I have to ask because that drawing isn't complete, and doesn't make sense the way it is portrayed. (I'm not saying your wrong, just that it doesn't make sense. Somebody could have done something weird before you got to it.)

Yes, it's a single switch system. The previous owner did a lot of his own work in the basement.
I can see the wires, they are run along the joists so I've verified the run to the switch. I haven't pulled
the fixtures out to see the connections, the wires in my "diagram."

I opened up the fixtures to see what he did, here's a better representation. I've left the grounds out.
In the pull switch fixture, he's using that box as a junction. In addition to the source, there are three
outgoing lines (including the line for the switched light). He's got a pigtail from three of the lines
going to the light fixture, and he as the wires to the switched light fixture connected to the pull string
fixture.


Here's some more brilliant artwork:

Hmmm, I think I see what's going on.

Let's call the line coming in as "Circuit A" with a branch coming off of it at the fixture (CL for Chain Light) to the other stuff, and the loop to the switchable light (SL) as "Circuit B." You want that first light to be part of the loop of Circuit B rather than Circuit A.

Commence with more brilliant drawings!



Bet money the branching line off that chain light is tagged right into the fixture. One Internet Dollar.

So you'll have to isolate that CL from the main line coming in and make it dependent on line feeding through the switch.

Bypass the hot coming through the CL - could be as easy as unfastening it and running some electrical tape around it, depending on how dodgy the wiring job was.

Run a hot wire from the SL to the hot wire post of the CL. Done.

[edit]

Posted this as you were posting (had to do some work on the brilliant drawings). One Internet Dollar won!

Oh, I've got hot as red and ground as black here. Might as well spend the two dollars at Home Depot and get a junction box for the branching off stuff. Sparky spark demons are evil things and sometimes like to hop around electrical tape splices.

Ok, was hoping for a quick fix using existing wiring, but it seems like it ain't gonna work that way.

So how's this look to you:

Add a junction box to take care of the variety of lines coming in. Out of the junction box, run some 14-3 wire. Black (hot) goes all the way to the switch.
Red connects the two fixtures, terminates with a wire nut on the unused end. White goes from junction box to both fixtures. The switches hot return line
comes to the currently switched light.

The existing between the switched light and the switch is 2 wire - white goes to the switch, black returns to the light. By using three wire line from the junction
to the switched light, I'll be able to connect the two lights and run the hot line all the way to the switch without too much hassle.

Looks like I've got a trip to Home Depot ahead of me!

Of course, this thread needs as much brilliant artwork as it can get, so here goes (I put each section of wire I'll need to run in boxes, more for myself than
anthing else):

My electrical experience for you:

Ahh but the artwork is BRILLIANT!!!

I'll also point out it's the most easily understood of the representations presented here.



The Jedi Master

If Picasso drew that it would be worth millions today.

I like the junction box solution.

If it were me I'd also factor in another hour of troubleshooting it at the end as the Chain Light just won't work. Run the wires again, check the splices, maybe replace the switch.

And then pull the chain on the light to find out it was in the off position the whole time.

Slap forehead repeatedly.

I was going to get a new fixture to replace the chain fixture for JUST that reason!!

Well, mission accomplished! I did use the junction box, and replaced the chain pull fixture (both fixtures, really, they were plastic and I got porcelain). Wifey happy now!

Random safety tip in the off chance its needed: Make absolutely 100% for certain without a doubt you have the wires to the chain fixture in properly. If you reverse the hot and neutral, everything will still appear to work, and if you're insulated you might not notice anything at all, but the chain will be connected to the hot line, which is very bad. In so many older houses in particular, you get two different shades of greyish brown insulation on the wires. In a house done up by a DIY type, the colors are no guarantee anyways.

An idiot tester is invaluable:

http://www.amazon.com/GE-3-Wire-Receptac...+circuit+tester