GRGR 1,2 tracks

[Cometman]

> tracks imply a wheeled conveyance traveling over them. 

I also seem to recall that ..ahem...I've heard it mentioned that with
the intervention of certain chemicals, manifestations in the air were
visible and they were sometimes referred to as "tracks"

no, I guess that was "trails"
 
Still, it would be more economical for the theater if the tracks were
laid by the spectators