Fluid-based delay?

[Paul Perry]

At 11:57 AM 26/07/98 -0700, Ethan Duni wrote:
>-another similar interesting system i was told of was one where the tubes in
>question were filled with materials that conduct sound _more_ quickly than
>air, so you actually get a negative delay (though not a whole lot).  never
>heard whether it got built, though.  i think the idea was to use helium..
>could be wrong..
.....negative delay?
sounds like the legendary Precognita 100....

paul perry melbourne australlia