Transmission lines - which is which?

Hello,

I tried the advance search using "trans cooler" and "trans lines" and it didn't turn up anything. I have also googled for the answer, but found conflicting answers.

So, I will ask:

Which trans line going into the factory radiator is the feed line (hot line) and which line is the return line (cold line)? I tried touching them both, but they felt about the same to me.

My XJ is a 2000 Limited and it is completely stock (at least the cooling system is) except for bigger tires and a Rusty's K&N conical filter setup. The radiator is the original (155k miles).

In the bottom of the radiator, out the top.

See if this helps.