There is quite a bit of missing footage from the Cathedral scene. The cubs after first appearing, pulled out their muscle pads, inhaled, and then moved about at blazing speed. These pictures (courtesy of
www.logansrun.com) offer a glimpse of this deleted sequence:



Actor Gary Morgan (who portrayed Billy) says that this sequence was percisely choreographed and then filmed over and over. The camera was under-cranked and each time the actors performed it at a different speed. The intent was to add special effects to the footage in post production to make their movements look hyper fast. However no effect was found to properly "streak" the actors movements (remember this was 1976), and MGM probably didn't want to invest too much effort into a scene that depicted drug use among minors. Without any post production effects, the movements of the cubs looked comical (a la Keystone Cops) rather than menacing so the whole sequence was dropped from the film. Too bad since without this display of their power, the cubs come off as little more than a nuisance in the released edit of the film.
With the computerized special effects that are available today, just think how easily the streaking of the actors could be achieved. This is the sole instance where I would love to see modern special effects applied to original Logan's Run footage. If this sequence were finally finished and inserted back into the film, it would allow us to see the complete Cathedral scene as originally envisioned by director Michael Anderson.