I was waiting in a old courthouse hallway with alternating white marble and black granite tiles, when I noticed some interesting spirals etched on several of the black granite tiles. No cameras so no picture but I can describe it fairly simply, I think, since I have basic understanding of the operation and physics of rotating floor buffer in gyroscopic equilibrium. The spirals don't appear to be very common for such an old, over-buffed to "bull-nosed like" tile edges, so I take that to mean there are specific density and diameter particles responsible which I think corresponds to the ~6mm-8mm circle of origin from which the spiral emanates increasing outward to 20-30 mm separation after 2-3 revolutions. (fairly analogous to a seashell spiral) It could start at the largest radius and decrease radius inward to a circle and that is probably what is causing my dilemma... I don't even know which direction makes sense! So why not work it through both ways. From what a remember of "playing" with an old-fashioned floor buffer as a child when you "hit" a hard particle (obviously I was not doing it correctly) the buffer jerks quite forcefully and it is thrown out of equilibrium. I would obviously let go of the switch and after a short time the buffer comes to a stop. I would remove the pebble and go back to "buffing". The one thing I am sure about is that the center circles were etched much more deeply than the thin line of the spiral which leads into or spirals out from the entire buffer rotating off-center for a number of revolutions. Can anyone say for certain which direction makes more logical sense or if either way works the same?