I have a fun tangential story about when steam doesn't rise. In college I would walk past a steam stack on campus every day, because I could see it was always

I have a fun tangential story about when steam doesn't rise. In college I would walk past a steam stack on campus every day, because I could see it was always on the verge of making rings (pretty much any cylinder with steam or smoke passing through it or around it is, I've seen rings from incense, boiling rice [the cylinder here is the column of steam bubbles], dropping food coloring into water - if you look for them you start finding them. The craziest example I've seen, which works much like the food coloring, is an airplane contrail.). I thought if I kept it up, one day the wind would blow in just right right way and there would be a beautiful train of rings. I never did see it. But on a hot day[1], I saw the steam settle into the narrow alley next to the building. It formed into a tiny roll cloud, about six feet long. I watch it stunned for about fifteen seconds, and then it dispersed. [1] I'm pretty sure it was a hot day, what I remember clearly was that it was an unusual temperature. I surmise the air was very warm and so the steam was denser than the air. But it may have been a cold day and the steam cooled and then sank, unfortunately I can't say for sure because I didn't write it down.