I made a couple of comments in pipeguy's question about meerschaum liners (stummels channel), the last being that I once had a pipe with a pyrolitic graphite liner.
That woke up my brain and I did some searching and came across a fascinating site dedicated to The Pipe and The Smoke. http://www.thepipe.info
This site tells the whole story behind these pipes. After seeing the shapes I remembered mine was a blue "Berkeley" (gotta remember this was the 70's). I was living in KC at the time and I ordered it thru some magazine. I probably still have the thing buried somewhere in all my crap. There is a cutaway view of innards and the venturi airway brings to mind the reverse Calabash principle being employed by some today. One of the things they touted was being able to smoke all the tobacco to the bottom. Maybe it was just me but every time I tried that I would get light headed to the point of wanting to cough my cookies. I finally put the thing away and went back to wood.
One has to give credit as this was probably the most successful of all the pipe gimmicks that have been tried over the years.
Chas.