Silent rocking 4ft silver sphere hovering 2ft of the ground with tremendous takeoff speed.

In 1975 I was a marine stationed at Camp Lejeune. North Carolina. I was a military policeman and was working the graveyard shift with my partner. 
As we turned down this certain street I noticed a silvery light about 100 yards away on the left side of the road.I told my partner to check it out and to keep his eyes on it since I was driving.  As we got within 50 yards or so I could not figured out what the light was. 
I thought that maybe, since the light was near a trash dumpster, that an scavanging animal had maybe pulled out a plastic bag and it was reflecting back our headlight beams. This part of the base is near a wooded area right next to a large inlet of water, so I thought that my animal theory was probably correct. 
When we got to about 25 yards away from the light to my surprise it was not an animal with plastic trash bag but a silvery color sphere about approximately 48 to 60 inches wide.  It hovered off the ground approximately 2 ft.  It made no noise and just kinda floated just a bit to and fro.
By this time I had slowed my patrol vehicle to less than 5 miles per hour and was slowly inching our way towards the sphere.  At about 10 yards away from the object, I got a good look at it.  It didnot have a smooth surface but rather a surfaced made of crumpled tin foil and every time it shifted positions it would reflect our headlight beams.
By this time my partner was mesmerized he seem to be in a trance and would not answer my questions.  At this time I grabbed hold of my spotlight control and aimed at the object. The object began to move to the edge of the road. I then shot it with the spotlight beam and the object stopped and rotated on its axis several times and than shot across the road at a tremendous rate of speed.
It was so fast that one second it was right in front of us then it was gone leaving like a trail of light behind it. ''
It dissappeared into a patch of trees. I had been in radio communications with my Desk Sargeant who had dispatched some backup patrols to my location but they got there to late.
After searching the area for more than an hour we finally call it quits and I went back to the station to submit my report.  
All this time my partner never spoke a word he was in some kind of shock.
Witness indicates that the date of the incident is approximate.  PD