Dust Devils
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In 1775, Benjamin Franklin was riding through the Maryland countryside when he observed something he described as a conical, sugar-loaf shape, its smaller part near the ground but widening upwards. He estimated it to measure 40 to 50 feet high and 20 to 30 feet in diameter. Its forward motion kept neither a straight path nor uniform motion, but made little zigzags as it went along in a cloud of leaves and dust.

What weather phenomenon did Franklin see? Bill Christianson, from Omaha, Nebraska phoned in the correct answer.

I think what Franklin probably saw (from your description of it) would be what we call a dust devil. I would imagine it is similar to a tornado in a sense because it goes around circularly, but it is not nearly as big and of course not nearly as destructive. (We see them quite often out here and in many parts of the country, I know.) It is simply a little whirlwind.

A dust devil is a rotating column of air made visible by dust, sand, and debris. They have been as tall as 1,645 feet and are typically between 10 and 100 feet wide.

Orin Helbauch, from Scranton, Pennsylvania, explained why Franklin probably saw his dust devil.

(I believe that Benjamin Franklin and his friends saw a whirlwind or dust devil while they were traveling.) I would guess that it was in the summer time and because of a very hot day, there was some very hot ground, which created the conditions for a whirlwind. The cooler air above and the warmer ground below just got things all swirled up.

On hot, sunny days with light winds, air temperatures can differ by 10 or 15 degrees from a field to a pond to woods or other places. This makes little whirlpools of warm and cold air. When jostled by even the tiniest breeze, they whip up into a swirl for a few seconds or several minutes and create a dust devil.