Saucer with no sound flew 100 feet above ground, changed direction then left atmosphere in a split second.

This was in the fall of 1967.  We were sitting in a park when we notice the craft slowly fly over the top of us approximately 100' above the ground.  It made no sound.  It was approximately 1/4 the size of a city block in circumference (approximately 100').  As it traveled away we could see that it was soucer shape.  The craft had markings on the bottom, but I can not remember exactly what they looked like.  We could see the shape easily because of the reflection of the street lights and the clear starry night sky.  We watched it follow the street (due south) for approximately one quarter mile it cruised at a speed of approximately 20 mph, at which point it made an immediate change in direction to the southwest and shot out of the sky into the atmosphere within about a second.  There were no lights or sound.  It was mid week and no one else was around.  There was no traffic or other witnesses that we know of.  Neither of us has mentioned this or reported this information.  To this day I have not seen anything that resembles the appearance of characteristics of this craft.  None of the characteristics below apply.
((ADDENDUM FROM WITNESS, DATED OCTOBER 23, 2008))
Correction:  Report dated 10-1-67 "Saucer with no sound flew 100 feet above ground, changed direction then left atmosphere in a split second." was actually in October "1966".