Bubbles coming out the chimney!

I know this is likely to sound like I'm smoking something, but I'm not. The other day I was burning my Woodstock Classic, which of course has a catalytic combustor. It was a sunny day and I was outside doing something and happened to look up at the chimney. The sun was shining from behind the chimney and was shielded by the eve of the house, so I wasn't looking directly into it. When I looked at the chimney I could see smoke or water vapor coming out the top, but also I saw what looked like the occasional small bubble like from kids blowing bubbles. I was really shocked and thought at first that my eyes were playing tricks on me. You know how you see small dots moving across your line of site after you rub your eyes? But no, I blinked and shifted my perspective and the bubbles continued to float away up into the sky. They behaved just like real bubbles would with that strange dancing movement they make from slight wind currents.

I walked around to the other side of the house to see if I could get a better view, but with the sun at my back all I could see was heat shimmers coming out the top of the stack. When I got back to my original viewing angle I could again see the smoke/water vapor billowing out with the occasional bubble floating off into the sky! Has anyone ever seen such a phenomenon? Any ideas what it might have been? I can't imagine anything could pass through a fired off cat and still be able to produce an actual bubble.

Hey HollowHill,
Thanks for the first serious response. I think you might be onto something, because while I did not think to mention it in my OP I did see long spider webs floating away around the chimney at the same time and it struck me as odd that they would be floating so high up in the air and just be a single strand of spider web. We are surrounded by forest and lots of spiders during warmer weather, but not so much after the freezes we've had. That was another reason the spider web seemed odd to me.

Okay, let me try to give you a better idea of what the bubbles looked like. I'm not talking about a bubble machine spewing out a ton of big bubbles. What was rising from the area of the chimney was so minuscule that at first I thought it was an artifact on the surface of my eye like you get after you rub your eye and you see those little dots floating across your field of vision. I'm calling what I saw "bubbles" because that description is the closest thing I can think of to describe what I saw. They were so small that I could just barely make them out. However, they danced around like bubbles do when you see a kid blowing them outdoors and the air currents are pushing them around in crazy movements. Sort of swirling upwards instead of floating in a straight line. What was also a bit odd is that while they were very small I could watch them float upwards at least 50 - 75 feet and they didn't seem to change much in size while they rose up.