Yesterday'S fool in this column was - no, not me - Feste, from Twelfth Night. Today's shall be Touchstone in As You Like It who, according to Jaques, had much in common with some meteorologists:
And in his brain he hath strange places cramm'd
With observation, the which he vents
In many mangled forms.
Like yesterday, today's story relates to the way in which things dry. Some years ago, a man with an inquiring mind noticed how the rain evaporates from roads when showers have passed. When dry, most roads are grey or blue, or perhaps a pastel shade of pink; when wet they have a darker colour, but as the surface dries, it gradually reverts to its original and lighter shade.
Now, our observer's attention was particularly drawn to a road adorned with a central broken white line. One particular side of all the line segments was the first to dry, appearing for a time brighter in colour than the remainder of the road; in the blank spaces in between, the road dried more slowly but quite uniformly throughout its entire width, and at the same rate as the "wet" side of the white line segments.
Consequently, dry bright rectangles appeared on one side of all the segments, while the rest of the road was dark and wet. He took a photograph and showed it to a meteorologist.
The latter decided that a fresh breeze must be blowing at right angles to the road. He noted that each white stripe projected several millimetres above the surface of the road, so this obstruction, he opined, must be causing a turbulent wake downwind as the wind blew over it. This increased turbulent mixing in the air very near the ground would accelerate the rate of drying in the way we noted yesterday, producing a dry area in the lee of the white lines.
But a colleague, looking at the photograph, was not convinced. "O noble fool!," he said, "O worthy fool! Motley's the only wear." And went on give his own much simpler explanation.
He noted that the photograph was taken on a curve, and that the road was cambered. The projecting segments of white line, he said, were little dams. The areas downslope of the line segments were protected from run-off from the "upper" side of the road, and with less water dried more quickly than elsewhere.
Moreover, the impeded water was constrained to flow around the ends of the white lines, adding further to the wetness of the downslope areas not protected in this way - and thus the differential rates at which various sectors of the road began to dry.