The Difference Between the 19th and 20th centuries in one picture

 Francis Galton and Karl Pearson (from 1909).  This picture is rather amusing because we have a man clearly of the 20th century (Karl Pearson) and then next to him Francis Galton is wearing gloves, a blanket, umbrella, and a hat: Galton knows he looks like a Dickens character and doesn't care.  Which tells us something about the personality of Francis Galton.