carburetor question

[tooge]

Ok, so I've got a four cylinder F head engine on my old jeep. I'm replacing the carb with a Holley 1908 carb since it is a direct bolt on and has a lower profile. Anyhow, does anyone know what that line is that goes into the carb base? It's basically coming up from the bottom of the pic and going into the top of the intake/bottom of carb. It isn't the fuel line. Help? thx.