A ball of blue-white fire rolls on the roadway, and kills my engine.On 9 Feb, 04,at 18:00 or so I was driving North on Highway 4 in Iowa, just south of Wallingford and North of Graettinger. There, Highway 4 is two-lane, and twisty. It has an upward grade on the West side and a valley to the East and the road goes slightly to the NnE. Because Highway 4 is winding and visibility is low at this point, I was driving slowly (40mph or less) when I saw a small ball of Blue-white light to the west side of the road, apparantly coming towards me. The west (left) side has a grade that goes up steeply, and whatever it was would either have to go up the hill or onto the road.I slowed further and pulled to the centre of the road. At first I thought it was someone on a snomobile outing, but it was the twilight of day and I saw no snomobile, but just the light. The ball of light, as it turned up to be, came onto the roadway from the west side, and rolled in a SsE direction. It rolled over the Northewst (front driver) corner of my car and across the hood. It did not burn the paint or make sparks off of the car. The ball rolled up the hood and spread out over the windshield. My radio ariel is inside of the windsheild as wires in the glass so there were no sparks from it, either. As the ball passed over the center rear of the hood the engine died cold, although the car continued to roll of its own momentum. The dashboard lamps and headlamps went out, and the radio went off. The ball passed over the roof of the car and rolled down the back window, and across the trunk and off of the southeast (rear passanger) corner of the car. I can't be sure I heard it make a sound, if it made a sound it was like a plastic grocery bag rattling if you crumpled it up. I looked in my mirror and saw as it rolled southward a short distance (30-40 feet)down the center of the road and rolled off the East (right) side of the road into the valley below, where I lost sight of it. I turned my key off and turned it back on, and as the car was still rolling and in gear the motor started up, although the headlamps and dash lamps were dim for a few miles. By the time I had reached Estherville (Ten Miles North) the headlamps and dashboard lamps were brighter, and I continued on to Spirit Lake via Highway 9. By the time I reached Spirit Lake (about 20 miles West) all of the lamps and the like seemed to work, but my presets on the radio had to be reset, and the clock was wrong. The ball of light left no marks on my car's paint or the vinyl roof, and as my car is old enough not to have a computer in it (1978) there seem to be no lasting effects. I was physically unharmed, except that I had "flash bulb syndrome" (a ghost of the light was showing up as an after effect) for ten miles or so, and some metal fillings in my teeth hurt for a few days.