It was a dark and stormy night when R. H. Bing volunteered to
drive some stranded mathematicians from the fogged-in Madison
airport to Chicago. Freezing rain pelted the windscreen and iced
the roadway as Bing drove on--concentrating deeply on the
mathematical theorem he was explaining. Soon the windshield
was fogged from the energetic explanation. The passengers too
had beaded brows, but their sweat arose from fear. As the
mathematical description got brighter, the visibility got dimmer.
Finally, the conferees felt a trace of hope for their survival when
Bing reached forward--apparently to wipe off the the moisture
from the windshield. Their hope turned to horror when, instead,
Bing drew a figure with his finger on the foggy pane and
continued his proof--embellishing the illustration with arrows and
helpful labels as needed for the demonstration.