Hey guys can someone tell me how the oil leaks when you have a leaking distributor o-ring?

I had been thinking my head gasket was leaking on my built motor with 5K miles, But I kept driving it,

Tonight I started inspecting this trying to find my problem, And on the BOTTOM of the distributor cap, its coated in oil, forming a drip.

How does the O-ring usually leak, Does it run down the cap or down the block or what?